<一>函数模板(函数模拟图)

函数模板 模板的意义:对类型也参数化 int sum1(int a,int b){return a+b;} double sum2(double a ,double b){return a+b;} 几个概念 函数模板 模板的实例化 模板函数 模板类型参数 模板非类型参数 模板实参推演 模板的特例化 ...

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函数模板模板的意义:对类型也参数化int sum1(int a,int b){return a+b;}double sum2(double a ,double b){return a+b;}

几个概念函数模板模板的实例化模板函数

模板类型参数模板非类型参数

模板实参推演模板的特例化模板函数,模板的特例化,非模板函数的重载关系

点击查看代码template<typename T,typename E> //定义一个模板参数列表 或者用 class T 也可以bool compare(T x ){ //compare 是一个函数模板，它目前只是个模板 cout<<"Template Compare"<<endl; return x>y;}int main(){ //函数的调用点,在函数调用点,编译器用用户指定的类型,从原模板实例化一份函数代码出来 // bool compare<int>(int a,int b){return a>b;} 这个从模板实例化出来的函数 就叫模板函数 // bool compare<double>(double a, double b){return a>b} 这个从模板实例化出来的函数 就叫模板函数 //模板函数是编译器根据指定的类型从模板实例化出来 参与编译的函数 //从用户的角度来看，我们只写了一份模板代码,代码量是变少了,但是对于编译器来说,需要编译的代码没有减少,都需要根据指定的类型实例化出来具体函数 compare<int>(1,2);// compare(100,200);//也可以,编译器会根据实参类型进行推演出 compare<int> 进行模板的实例化. //注意如果有compare<int>(1,2); 然后有compare(100,200); //编译器不会生成两套同样的 bool compare<int>(int a,int b){return a>b;},因为这个函数是需要在编译期间生成符号表, //如果生成两次,会出现在符号表中重名问题 return 1;}

示例代码2 不实例话模板 并查看编译后.o文件中的 符号表情况

点击查看代码#include <iostream>using namespace std;template<typename T>bool compare(T x,T y){ return x,y;}int main(){ return 1;}//编译后查看.o文件中的符号表信息如下 符号表中看不到compare函数的符号kl@kl-ThinkPad-T580:/data/usershare/code/compile$ objdump -t test1.otest1.o： 文件格式 elf64-x86-64SYMBOL TABLE:0000000000000318 l d .interp 0000000000000000 .interp0000000000000338 l d .note.gnu.property 0000000000000000 .note.gnu.property0000000000000358 l d .note.gnu.build-id 0000000000000000 .note.gnu.build-id000000000000037c l d .note.ABI-tag 0000000000000000 .note.ABI-tag00000000000003a0 l d .gnu.hash 0000000000000000 .gnu.hash00000000000003c8 l d .dynsym 0000000000000000 .dynsym00000000000004a0 l d .dynstr 0000000000000000 .dynstr0000000000000576 l d .gnu.version 0000000000000000 .gnu.version0000000000000588 l d .gnu.version_r 0000000000000000 .gnu.version_r00000000000005c8 l d .rela.dyn 0000000000000000 .rela.dyn00000000000006b8 l d .rela.plt 0000000000000000 .rela.plt0000000000001000 l d .init 0000000000000000 .init0000000000001020 l d .plt 0000000000000000 .plt0000000000001050 l d .plt.got 0000000000000000 .plt.got0000000000001060 l d .plt.sec 0000000000000000 .plt.sec0000000000001080 l d .text 0000000000000000 .text0000000000001258 l d .fini 0000000000000000 .fini0000000000002000 l d .rodata 0000000000000000 .rodata0000000000002008 l d .eh_frame_hdr 0000000000000000 .eh_frame_hdr0000000000002060 l d .eh_frame 0000000000000000 .eh_frame0000000000003d90 l d .init_array 0000000000000000 .init_array0000000000003da0 l d .fini_array 0000000000000000 .fini_array0000000000003da8 l d .dynamic 0000000000000000 .dynamic0000000000003fa8 l d .got 0000000000000000 .got0000000000004000 l d .data 0000000000000000 .data0000000000004010 l d .bss 0000000000000000 .bss0000000000000000 l d .comment 0000000000000000 .comment0000000000000000 l df *ABS* 0000000000000000 crtstuff.c00000000000010b0 l F .text 0000000000000000 deregister_tm_clones00000000000010e0 l F .text 0000000000000000 register_tm_clones0000000000001120 l F .text 0000000000000000 __do_global_dtors_aux0000000000004010 l O .bss 0000000000000001 completed.80590000000000003da0 l O .fini_array 0000000000000000 __do_global_dtors_aux_fini_array_entry0000000000001160 l F .text 0000000000000000 frame_dummy0000000000003d90 l O .init_array 0000000000000000 __frame_dummy_init_array_entry0000000000000000 l df *ABS* 0000000000000000 TemplateTest1.cpp0000000000002004 l O .rodata 0000000000000001 _ZStL19piecewise_construct0000000000004011 l O .bss 0000000000000001 _ZStL8__ioinit0000000000001178 l F .text 000000000000004d _Z41__static_initialization_and_destruction_0ii00000000000011c5 l F .text 0000000000000019 _GLOBAL__sub_I_main0000000000000000 l df *ABS* 0000000000000000 crtstuff.c00000000000021a4 l O .eh_frame 0000000000000000 __FRAME_END__0000000000000000 l df *ABS* 0000000000000000 0000000000002008 l .eh_frame_hdr 0000000000000000 __GNU_EH_FRAME_HDR0000000000001000 l F .init 0000000000000000 _init0000000000003da8 l O .dynamic 0000000000000000 _DYNAMIC0000000000003da0 l .init_array 0000000000000000 __init_array_end0000000000003d90 l .init_array 0000000000000000 __init_array_start0000000000003fa8 l O .got 0000000000000000 _GLOBAL_OFFSET_TABLE_0000000000004010 g .data 0000000000000000 _edata0000000000004000 w .data 0000000000000000 data_start0000000000002000 g O .rodata 0000000000000004 _IO_stdin_used0000000000000000 w F *UND* 0000000000000000 __cxa_finalize@@GLIBC_2.2.50000000000001169 g F .text 000000000000000f main0000000000004008 g O .data 0000000000000000 .hidden __dso_handle0000000000001258 g F .fini 0000000000000000 .hidden _fini0000000000000000 F *UND* 0000000000000000 __cxa_atexit@@GLIBC_2.2.50000000000001080 g F .text 000000000000002f _start0000000000004010 g O .data 0000000000000000 .hidden __TMC_END__0000000000004000 g .data 0000000000000000 __data_start0000000000004018 g .bss 0000000000000000 _end0000000000004010 g .bss 0000000000000000 __bss_start0000000000000000 F *UND* 0000000000000000 _ZNSt8ios_base4InitC1Ev@@GLIBCXX_3.400000000000011e0 g F .text 0000000000000065 __libc_csu_init0000000000000000 w *UND* 0000000000000000 _ITM_deregisterTMCloneTable0000000000001250 g F .text 0000000000000005 __libc_csu_fini0000000000000000 F *UND* 0000000000000000 __libc_start_main@@GLIBC_2.2.50000000000000000 w *UND* 0000000000000000 __gmon_start__0000000000000000 w *UND* 0000000000000000 _ITM_registerTMCloneTable0000000000000000 F *UND* 0000000000000000 _ZNSt8ios_base4InitD1Ev@@GLIBCXX_3.4

示例代码3 实例化模板 并查看编译后.o文件中的 符号表情况

点击查看代码#include <iostream>using namespace std;template<typename T>bool compare(T x,T y){ return x,y;}int main(){ bool b=compare<int>(100,200); return 1;}//编译生成.o文件,查看其中的符号表信息, 在其中找到了 compare函数的符号表kl@kl-ThinkPad-T580:/data/usershare/code/compile$ objdump -t test1.otest1.o： 文件格式 elf64-x86-64SYMBOL TABLE:0000000000000318 l d .interp 0000000000000000 .interp0000000000000338 l d .note.gnu.property 0000000000000000 .note.gnu.property0000000000000358 l d .note.gnu.build-id 0000000000000000 .note.gnu.build-id000000000000037c l d .note.ABI-tag 0000000000000000 .note.ABI-tag00000000000003a0 l d .gnu.hash 0000000000000000 .gnu.hash00000000000003c8 l d .dynsym 0000000000000000 .dynsym00000000000004a0 l d .dynstr 0000000000000000 .dynstr0000000000000576 l d .gnu.version 0000000000000000 .gnu.version0000000000000588 l d .gnu.version_r 0000000000000000 .gnu.version_r00000000000005c8 l d .rela.dyn 0000000000000000 .rela.dyn00000000000006b8 l d .rela.plt 0000000000000000 .rela.plt0000000000001000 l d .init 0000000000000000 .init0000000000001020 l d .plt 0000000000000000 .plt0000000000001050 l d .plt.got 0000000000000000 .plt.got0000000000001060 l d .plt.sec 0000000000000000 .plt.sec0000000000001080 l d .text 0000000000000000 .text0000000000001288 l d .fini 0000000000000000 .fini0000000000002000 l d .rodata 0000000000000000 .rodata0000000000002008 l d .eh_frame_hdr 0000000000000000 .eh_frame_hdr0000000000002068 l d .eh_frame 0000000000000000 .eh_frame0000000000003d90 l d .init_array 0000000000000000 .init_array0000000000003da0 l d .fini_array 0000000000000000 .fini_array0000000000003da8 l d .dynamic 0000000000000000 .dynamic0000000000003fa8 l d .got 0000000000000000 .got0000000000004000 l d .data 0000000000000000 .data0000000000004010 l d .bss 0000000000000000 .bss0000000000000000 l d .comment 0000000000000000 .comment0000000000000000 l df *ABS* 0000000000000000 crtstuff.c00000000000010b0 l F .text 0000000000000000 deregister_tm_clones00000000000010e0 l F .text 0000000000000000 register_tm_clones0000000000001120 l F .text 0000000000000000 __do_global_dtors_aux0000000000004010 l O .bss 0000000000000001 completed.80590000000000003da0 l O .fini_array 0000000000000000 __do_global_dtors_aux_fini_array_entry0000000000001160 l F .text 0000000000000000 frame_dummy0000000000003d90 l O .init_array 0000000000000000 __frame_dummy_init_array_entry0000000000000000 l df *ABS* 0000000000000000 TemplateTest1.cpp0000000000002004 l O .rodata 0000000000000001 _ZStL19piecewise_construct0000000000004011 l O .bss 0000000000000001 _ZStL8__ioinit000000000000118e l F .text 000000000000004d _Z41__static_initialization_and_destruction_0ii00000000000011db l F .text 0000000000000019 _GLOBAL__sub_I_main0000000000000000 l df *ABS* 0000000000000000 crtstuff.c00000000000021cc l O .eh_frame 0000000000000000 __FRAME_END__0000000000000000 l df *ABS* 0000000000000000 0000000000002008 l .eh_frame_hdr 0000000000000000 __GNU_EH_FRAME_HDR0000000000001000 l F .init 0000000000000000 _init0000000000003da8 l O .dynamic 0000000000000000 _DYNAMIC0000000000003da0 l .init_array 0000000000000000 __init_array_end0000000000003d90 l .init_array 0000000000000000 __init_array_start0000000000003fa8 l O .got 0000000000000000 _GLOBAL_OFFSET_TABLE_0000000000004010 g .data 0000000000000000 _edata00000000000011f4 w F .text 0000000000000017 _Z7compareIiEbT_S0_ //compare函数的符号0000000000004000 w .data 0000000000000000 data_start0000000000002000 g O .rodata 0000000000000004 _IO_stdin_used0000000000000000 w F *UND* 0000000000000000 __cxa_finalize@@GLIBC_2.2.50000000000001169 g F .text 0000000000000025 main0000000000004008 g O .data 0000000000000000 .hidden __dso_handle0000000000001288 g F .fini 0000000000000000 .hidden _fini0000000000000000 F *UND* 0000000000000000 __cxa_atexit@@GLIBC_2.2.50000000000001080 g F .text 000000000000002f _start0000000000004010 g O .data 0000000000000000 .hidden __TMC_END__0000000000004000 g .data 0000000000000000 __data_start0000000000004018 g .bss 0000000000000000 _end0000000000004010 g .bss 0000000000000000 __bss_start0000000000000000 F *UND* 0000000000000000 _ZNSt8ios_base4InitC1Ev@@GLIBCXX_3.40000000000001210 g F .text 0000000000000065 __libc_csu_init0000000000000000 w *UND* 0000000000000000 _ITM_deregisterTMCloneTable0000000000001280 g F .text 0000000000000005 __libc_csu_fini0000000000000000 F *UND* 0000000000000000 __libc_start_main@@GLIBC_2.2.50000000000000000 w *UND* 0000000000000000 __gmon_start__0000000000000000 w *UND* 0000000000000000 _ITM_registerTMCloneTable0000000000000000 F *UND* 0000000000000000 _ZNSt8ios_base4InitD1Ev@@GLIBCXX_3.4

示例代码4 实例化2次模板一次指定类型,一次参数类型自动推演 两个类型是一样的情况下 并查看编译后.o文件中的 符号表情况

点击查看代码#include <iostream>using namespace std;template<typename T>bool compare(T x,T y){ return x,y;}int main(){ bool b =compare<int>(100,200); bool b2=compare(400,200); return 1;}//编译生成.o文件,查看其中的符号表信息, 在其中找到了一处compare函数的符号表kl@kl-ThinkPad-T580:/data/usershare/code/compile$ objdump -t test1.otest1.o： 文件格式 elf64-x86-64SYMBOL TABLE:0000000000000318 l d .interp 0000000000000000 .interp0000000000000338 l d .note.gnu.property 0000000000000000 .note.gnu.property0000000000000358 l d .note.gnu.build-id 0000000000000000 .note.gnu.build-id000000000000037c l d .note.ABI-tag 0000000000000000 .note.ABI-tag00000000000003a0 l d .gnu.hash 0000000000000000 .gnu.hash00000000000003c8 l d .dynsym 0000000000000000 .dynsym00000000000004a0 l d .dynstr 0000000000000000 .dynstr0000000000000576 l d .gnu.version 0000000000000000 .gnu.version0000000000000588 l d .gnu.version_r 0000000000000000 .gnu.version_r00000000000005c8 l d .rela.dyn 0000000000000000 .rela.dyn00000000000006b8 l d .rela.plt 0000000000000000 .rela.plt0000000000001000 l d .init 0000000000000000 .init0000000000001020 l d .plt 0000000000000000 .plt0000000000001050 l d .plt.got 0000000000000000 .plt.got0000000000001060 l d .plt.sec 0000000000000000 .plt.sec0000000000001080 l d .text 0000000000000000 .text0000000000001298 l d .fini 0000000000000000 .fini0000000000002000 l d .rodata 0000000000000000 .rodata0000000000002008 l d .eh_frame_hdr 0000000000000000 .eh_frame_hdr0000000000002068 l d .eh_frame 0000000000000000 .eh_frame0000000000003d90 l d .init_array 0000000000000000 .init_array0000000000003da0 l d .fini_array 0000000000000000 .fini_array0000000000003da8 l d .dynamic 0000000000000000 .dynamic0000000000003fa8 l d .got 0000000000000000 .got0000000000004000 l d .data 0000000000000000 .data0000000000004010 l d .bss 0000000000000000 .bss0000000000000000 l d .comment 0000000000000000 .comment0000000000000000 l df *ABS* 0000000000000000 crtstuff.c00000000000010b0 l F .text 0000000000000000 deregister_tm_clones00000000000010e0 l F .text 0000000000000000 register_tm_clones0000000000001120 l F .text 0000000000000000 __do_global_dtors_aux0000000000004010 l O .bss 0000000000000001 completed.80590000000000003da0 l O .fini_array 0000000000000000 __do_global_dtors_aux_fini_array_entry0000000000001160 l F .text 0000000000000000 frame_dummy0000000000003d90 l O .init_array 0000000000000000 __frame_dummy_init_array_entry0000000000000000 l df *ABS* 0000000000000000 TemplateTest1.cpp0000000000002004 l O .rodata 0000000000000001 _ZStL19piecewise_construct0000000000004011 l O .bss 0000000000000001 _ZStL8__ioinit00000000000011a0 l F .text 000000000000004d _Z41__static_initialization_and_destruction_0ii00000000000011ed l F .text 0000000000000019 _GLOBAL__sub_I_main0000000000000000 l df *ABS* 0000000000000000 crtstuff.c00000000000021cc l O .eh_frame 0000000000000000 __FRAME_END__0000000000000000 l df *ABS* 0000000000000000 0000000000002008 l .eh_frame_hdr 0000000000000000 __GNU_EH_FRAME_HDR0000000000001000 l F .init 0000000000000000 _init0000000000003da8 l O .dynamic 0000000000000000 _DYNAMIC0000000000003da0 l .init_array 0000000000000000 __init_array_end0000000000003d90 l .init_array 0000000000000000 __init_array_start0000000000003fa8 l O .got 0000000000000000 _GLOBAL_OFFSET_TABLE_0000000000004010 g .data 0000000000000000 _edata0000000000001206 w F .text 0000000000000017 _Z7compareIiEbT_S0_ //此处为compare的函数符号0000000000004000 w .data 0000000000000000 data_start0000000000002000 g O .rodata 0000000000000004 _IO_stdin_used0000000000000000 w F *UND* 0000000000000000 __cxa_finalize@@GLIBC_2.2.50000000000001169 g F .text 0000000000000037 main0000000000004008 g O .data 0000000000000000 .hidden __dso_handle0000000000001298 g F .fini 0000000000000000 .hidden _fini0000000000000000 F *UND* 0000000000000000 __cxa_atexit@@GLIBC_2.2.50000000000001080 g F .text 000000000000002f _start0000000000004010 g O .data 0000000000000000 .hidden __TMC_END__0000000000004000 g .data 0000000000000000 __data_start0000000000004018 g .bss 0000000000000000 _end0000000000004010 g .bss 0000000000000000 __bss_start0000000000000000 F *UND* 0000000000000000 _ZNSt8ios_base4InitC1Ev@@GLIBCXX_3.40000000000001220 g F .text 0000000000000065 __libc_csu_init0000000000000000 w *UND* 0000000000000000 _ITM_deregisterTMCloneTable0000000000001290 g F .text 0000000000000005 __libc_csu_fini0000000000000000 F *UND* 0000000000000000 __libc_start_main@@GLIBC_2.2.50000000000000000 w *UND* 0000000000000000 __gmon_start__0000000000000000 w *UND* 0000000000000000 _ITM_registerTMCloneTable0000000000000000 F *UND* 0000000000000000 _ZNSt8ios_base4InitD1Ev@@GLIBCXX_3.4

示例代码5 实例化2次模板 两次模板的参数类型不一样 并查看编译后.o文件中的 符号表情况

点击查看代码#include <iostream>using namespace std;template<typename T>bool compare(T x,T y){ return x,y;}int main(){ bool b =compare<int>(100,200); bool b2=compare(400,200); bool b3=compare<double>(1.0,2.0); return 1;}//编译生成.o文件,查看其中的符号表信息, 在其中找到了两处处compare函数的符号表,一次是int 一次是doublekl@kl-ThinkPad-T580:/data/usershare/code/compile$ g++ TemplateTest1.cpp -o test1.okl@kl-ThinkPad-T580:/data/usershare/code/compile$ objdump -t test1.otest1.o： 文件格式 elf64-x86-64SYMBOL TABLE:0000000000000318 l d .interp 0000000000000000 .interp0000000000000338 l d .note.gnu.property 0000000000000000 .note.gnu.property0000000000000358 l d .note.gnu.build-id 0000000000000000 .note.gnu.build-id000000000000037c l d .note.ABI-tag 0000000000000000 .note.ABI-tag00000000000003a0 l d .gnu.hash 0000000000000000 .gnu.hash00000000000003c8 l d .dynsym 0000000000000000 .dynsym00000000000004a0 l d .dynstr 0000000000000000 .dynstr0000000000000576 l d .gnu.version 0000000000000000 .gnu.version0000000000000588 l d .gnu.version_r 0000000000000000 .gnu.version_r00000000000005c8 l d .rela.dyn 0000000000000000 .rela.dyn00000000000006b8 l d .rela.plt 0000000000000000 .rela.plt0000000000001000 l d .init 0000000000000000 .init0000000000001020 l d .plt 0000000000000000 .plt0000000000001050 l d .plt.got 0000000000000000 .plt.got0000000000001060 l d .plt.sec 0000000000000000 .plt.sec0000000000001080 l d .text 0000000000000000 .text00000000000012e8 l d .fini 0000000000000000 .fini0000000000002000 l d .rodata 0000000000000000 .rodata0000000000002020 l d .eh_frame_hdr 0000000000000000 .eh_frame_hdr0000000000002088 l d .eh_frame 0000000000000000 .eh_frame0000000000003d90 l d .init_array 0000000000000000 .init_array0000000000003da0 l d .fini_array 0000000000000000 .fini_array0000000000003da8 l d .dynamic 0000000000000000 .dynamic0000000000003fa8 l d .got 0000000000000000 .got0000000000004000 l d .data 0000000000000000 .data0000000000004010 l d .bss 0000000000000000 .bss0000000000000000 l d .comment 0000000000000000 .comment0000000000000000 l df *ABS* 0000000000000000 crtstuff.c00000000000010b0 l F .text 0000000000000000 deregister_tm_clones00000000000010e0 l F .text 0000000000000000 register_tm_clones0000000000001120 l F .text 0000000000000000 __do_global_dtors_aux0000000000004010 l O .bss 0000000000000001 completed.80590000000000003da0 l O .fini_array 0000000000000000 __do_global_dtors_aux_fini_array_entry0000000000001160 l F .text 0000000000000000 frame_dummy0000000000003d90 l O .init_array 0000000000000000 __frame_dummy_init_array_entry0000000000000000 l df *ABS* 0000000000000000 TemplateTest1.cpp0000000000002008 l O .rodata 0000000000000001 _ZStL19piecewise_construct0000000000004011 l O .bss 0000000000000001 _ZStL8__ioinit00000000000011c0 l F .text 000000000000004d _Z41__static_initialization_and_destruction_0ii000000000000120d l F .text 0000000000000019 _GLOBAL__sub_I_main0000000000000000 l df *ABS* 0000000000000000 crtstuff.c000000000000220c l O .eh_frame 0000000000000000 __FRAME_END__0000000000000000 l df *ABS* 0000000000000000 0000000000002020 l .eh_frame_hdr 0000000000000000 __GNU_EH_FRAME_HDR0000000000001000 l F .init 0000000000000000 _init0000000000003da8 l O .dynamic 0000000000000000 _DYNAMIC0000000000003da0 l .init_array 0000000000000000 __init_array_end0000000000003d90 l .init_array 0000000000000000 __init_array_start0000000000003fa8 l O .got 0000000000000000 _GLOBAL_OFFSET_TABLE_0000000000004010 g .data 0000000000000000 _edata0000000000001226 w F .text 0000000000000017 _Z7compareIiEbT_S0_ //compare<int>(int a,int b) 函数符号0000000000004000 w .data 0000000000000000 data_start0000000000002000 g O .rodata 0000000000000004 _IO_stdin_used0000000000000000 w F *UND* 0000000000000000 __cxa_finalize@@GLIBC_2.2.50000000000001169 g F .text 0000000000000057 main0000000000004008 g O .data 0000000000000000 .hidden __dso_handle00000000000012e8 g F .fini 0000000000000000 .hidden _fini000000000000123d w F .text 0000000000000031 _Z7compareIdEbT_S0_ //compare<double>(double a ,double b) 函数符号0000000000000000 F *UND* 0000000000000000 __cxa_atexit@@GLIBC_2.2.50000000000001080 g F .text 000000000000002f _start0000000000004010 g O .data 0000000000000000 .hidden __TMC_END__0000000000004000 g .data 0000000000000000 __data_start0000000000004018 g .bss 0000000000000000 _end0000000000004010 g .bss 0000000000000000 __bss_start0000000000000000 F *UND* 0000000000000000 _ZNSt8ios_base4InitC1Ev@@GLIBCXX_3.40000000000001270 g F .text 0000000000000065 __libc_csu_init0000000000000000 w *UND* 0000000000000000 _ITM_deregisterTMCloneTable00000000000012e0 g F .text 0000000000000005 __libc_csu_fini0000000000000000 F *UND* 0000000000000000 __libc_start_main@@GLIBC_2.2.50000000000000000 w *UND* 0000000000000000 __gmon_start__0000000000000000 w *UND* 0000000000000000 _ITM_registerTMCloneTable0000000000000000 F *UND* 0000000000000000 _ZNSt8ios_base4InitD1Ev@@GLIBCXX_3.4//我们顺便看一下.o 文件生成的指令 kl@kl-ThinkPad-T580:/data/usershare/code/compile$ objdump -S test1.otest1.o： 文件格式 elf64-x86-64Disassembly of section .init:0000000000001000 <_init>: 1000: f3 0f 1e fa endbr64 1004: 48 83 ec 08 sub $0x8,%rsp 1008: 48 8b 05 d9 2f 00 00 mov 0x2fd9(%rip),%rax # 3fe8 <__gmon_start__> 100f: 48 85 c0 test %rax,%rax 1012: 74 02 je 1016 <_init+0x16> 1014: ff d0 callq *%rax 1016: 48 83 c4 08 add $0x8,%rsp 101a: c3 retq Disassembly of section .plt:0000000000001020 <.plt>: 1020: ff 35 8a 2f 00 00 pushq 0x2f8a(%rip) # 3fb0 <_GLOBAL_OFFSET_TABLE_+0x8> 1026: f2 ff 25 8b 2f 00 00 bnd jmpq *0x2f8b(%rip) # 3fb8 <_GLOBAL_OFFSET_TABLE_+0x10> 102d: 0f 1f 00 nopl (%rax) 1030: f3 0f 1e fa endbr64 1034: 68 00 00 00 00 pushq $0x0 1039: f2 e9 e1 ff ff ff bnd jmpq 1020 <.plt> 103f: 90 nop 1040: f3 0f 1e fa endbr64 1044: 68 01 00 00 00 pushq $0x1 1049: f2 e9 d1 ff ff ff bnd jmpq 1020 <.plt> 104f: 90 nopDisassembly of section .plt.got:0000000000001050 <__cxa_finalize@plt>: 1050: f3 0f 1e fa endbr64 1054: f2 ff 25 75 2f 00 00 bnd jmpq *0x2f75(%rip) # 3fd0 <__cxa_finalize@GLIBC_2.2.5> 105b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)Disassembly of section .plt.sec:0000000000001060 <__cxa_atexit@plt>: 1060: f3 0f 1e fa endbr64 1064: f2 ff 25 55 2f 00 00 bnd jmpq *0x2f55(%rip) # 3fc0 <__cxa_atexit@GLIBC_2.2.5> 106b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)0000000000001070 <_ZNSt8ios_base4InitC1Ev@plt>: 1070: f3 0f 1e fa endbr64 1074: f2 ff 25 4d 2f 00 00 bnd jmpq *0x2f4d(%rip) # 3fc8 <_ZNSt8ios_base4InitC1Ev@GLIBCXX_3.4> 107b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)Disassembly of section .text:0000000000001080 <_start>: 1080: f3 0f 1e fa endbr64 1084: 31 ed xor %ebp,%ebp 1086: 49 89 d1 mov %rdx,%r9 1089: 5e pop %rsi 108a: 48 89 e2 mov %rsp,%rdx 108d: 48 83 e4 f0 and $0xfffffffffffffff0,%rsp 1091: 50 push %rax 1092: 54 push %rsp 1093: 4c 8d 05 46 02 00 00 lea 0x246(%rip),%r8 # 12e0 <__libc_csu_fini> 109a: 48 8d 0d cf 01 00 00 lea 0x1cf(%rip),%rcx # 1270 <__libc_csu_init> 10a1: 48 8d 3d c1 00 00 00 lea 0xc1(%rip),%rdi # 1169 <main> 10a8: ff 15 32 2f 00 00 callq *0x2f32(%rip) # 3fe0 <__libc_start_main@GLIBC_2.2.5> 10ae: f4 hlt 10af: 90 nop00000000000010b0 <deregister_tm_clones>: 10b0: 48 8d 3d 59 2f 00 00 lea 0x2f59(%rip),%rdi # 4010 <__TMC_END__> 10b7: 48 8d 05 52 2f 00 00 lea 0x2f52(%rip),%rax # 4010 <__TMC_END__> 10be: 48 39 f8 cmp %rdi,%rax 10c1: 74 15 je 10d8 <deregister_tm_clones+0x28> 10c3: 48 8b 05 0e 2f 00 00 mov 0x2f0e(%rip),%rax # 3fd8 <_ITM_deregisterTMCloneTable> 10ca: 48 85 c0 test %rax,%rax 10cd: 74 09 je 10d8 <deregister_tm_clones+0x28> 10cf: ff e0 jmpq *%rax 10d1: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 10d8: c3 retq 10d9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)00000000000010e0 <register_tm_clones>: 10e0: 48 8d 3d 29 2f 00 00 lea 0x2f29(%rip),%rdi # 4010 <__TMC_END__> 10e7: 48 8d 35 22 2f 00 00 lea 0x2f22(%rip),%rsi # 4010 <__TMC_END__> 10ee: 48 29 fe sub %rdi,%rsi 10f1: 48 89 f0 mov %rsi,%rax 10f4: 48 c1 ee 3f shr $0x3f,%rsi 10f8: 48 c1 f8 03 sar $0x3,%rax 10fc: 48 01 c6 add %rax,%rsi 10ff: 48 d1 fe sar %rsi 1102: 74 14 je 1118 <register_tm_clones+0x38> 1104: 48 8b 05 e5 2e 00 00 mov 0x2ee5(%rip),%rax # 3ff0 <_ITM_registerTMCloneTable> 110b: 48 85 c0 test %rax,%rax 110e: 74 08 je 1118 <register_tm_clones+0x38> 1110: ff e0 jmpq *%rax 1112: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1) 1118: c3 retq 1119: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)0000000000001120 <__do_global_dtors_aux>: 1120: f3 0f 1e fa endbr64 1124: 80 3d e5 2e 00 00 00 cmpb $0x0,0x2ee5(%rip) # 4010 <__TMC_END__> 112b: 75 2b jne 1158 <__do_global_dtors_aux+0x38> 112d: 55 push %rbp 112e: 48 83 3d 9a 2e 00 00 cmpq $0x0,0x2e9a(%rip) # 3fd0 <__cxa_finalize@GLIBC_2.2.5> 1135: 00 1136: 48 89 e5 mov %rsp,%rbp 1139: 74 0c je 1147 <__do_global_dtors_aux+0x27> 113b: 48 8b 3d c6 2e 00 00 mov 0x2ec6(%rip),%rdi # 4008 <__dso_handle> 1142: e8 09 ff ff ff callq 1050 <__cxa_finalize@plt> 1147: e8 64 ff ff ff callq 10b0 <deregister_tm_clones> 114c: c6 05 bd 2e 00 00 01 movb $0x1,0x2ebd(%rip) # 4010 <__TMC_END__> 1153: 5d pop %rbp 1154: c3 retq 1155: 0f 1f 00 nopl (%rax) 1158: c3 retq 1159: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)0000000000001160 <frame_dummy>: 1160: f3 0f 1e fa endbr64 1164: e9 77 ff ff ff jmpq 10e0 <register_tm_clones>0000000000001169 <main>: 1169: f3 0f 1e fa endbr64 116d: 55 push %rbp 116e: 48 89 e5 mov %rsp,%rbp 1171: 48 83 ec 10 sub $0x10,%rsp 1175: be c8 00 00 00 mov $0xc8,%esi 117a: bf 64 00 00 00 mov $0x64,%edi 117f: e8 a2 00 00 00 callq 1226 <_Z7compareIiEbT_S0_> //compare<int>(100,200); 1184: 88 45 fd mov %al,-0x3(%rbp) 1187: be c8 00 00 00 mov $0xc8,%esi 118c: bf 90 01 00 00 mov $0x190,%edi 1191: e8 90 00 00 00 callq 1226 <_Z7compareIiEbT_S0_> //compare(400,200); 和上面调用的函数是一个函数 1196: 88 45 fe mov %al,-0x2(%rbp) 1199: f2 0f 10 05 6f 0e 00 movsd 0xe6f(%rip),%xmm0 # 2010 <_ZStL19piecewise_construct+0x8> 11a0: 00 11a1: 48 8b 05 70 0e 00 00 mov 0xe70(%rip),%rax # 2018 <_ZStL19piecewise_construct+0x10> 11a8: 66 0f 28 c8 movapd %xmm0,%xmm1 11ac: 66 48 0f 6e c0 movq %rax,%xmm0 11b1: e8 87 00 00 00 callq 123d <_Z7compareIdEbT_S0_> // bool b3=compare<double>(1.0,2.0); double 类型的函数 11b6: 88 45 ff mov %al,-0x1(%rbp) 11b9: b8 01 00 00 00 mov $0x1,%eax 11be: c9 leaveq 11bf: c3 retq 00000000000011c0 <_Z41__static_initialization_and_destruction_0ii>: 11c0: f3 0f 1e fa endbr64 11c4: 55 push %rbp 11c5: 48 89 e5 mov %rsp,%rbp 11c8: 48 83 ec 10 sub $0x10,%rsp 11cc: 89 7d fc mov %edi,-0x4(%rbp) 11cf: 89 75 f8 mov %esi,-0x8(%rbp) 11d2: 83 7d fc 01 cmpl $0x1,-0x4(%rbp) 11d6: 75 32 jne 120a <_Z41__static_initialization_and_destruction_0ii+0x4a> 11d8: 81 7d f8 ff ff 00 00 cmpl $0xffff,-0x8(%rbp) 11df: 75 29 jne 120a <_Z41__static_initialization_and_destruction_0ii+0x4a> 11e1: 48 8d 3d 29 2e 00 00 lea 0x2e29(%rip),%rdi # 4011 <_ZStL8__ioinit> 11e8: e8 83 fe ff ff callq 1070 <_ZNSt8ios_base4InitC1Ev@plt> 11ed: 48 8d 15 14 2e 00 00 lea 0x2e14(%rip),%rdx # 4008 <__dso_handle> 11f4: 48 8d 35 16 2e 00 00 lea 0x2e16(%rip),%rsi # 4011 <_ZStL8__ioinit> 11fb: 48 8b 05 f6 2d 00 00 mov 0x2df6(%rip),%rax # 3ff8 <_ZNSt8ios_base4InitD1Ev@GLIBCXX_3.4> 1202: 48 89 c7 mov %rax,%rdi 1205: e8 56 fe ff ff callq 1060 <__cxa_atexit@plt> 120a: 90 nop 120b: c9 leaveq 120c: c3 retq 000000000000120d <_GLOBAL__sub_I_main>: 120d: f3 0f 1e fa endbr64 1211: 55 push %rbp 1212: 48 89 e5 mov %rsp,%rbp 1215: be ff ff 00 00 mov $0xffff,%esi 121a: bf 01 00 00 00 mov $0x1,%edi 121f: e8 9c ff ff ff callq 11c0 <_Z41__static_initialization_and_destruction_0ii> 1224: 5d pop %rbp 1225: c3 retq 0000000000001226 <_Z7compareIiEbT_S0_>: // compare<int>(int a, int b) 1226: f3 0f 1e fa endbr64 122a: 55 push %rbp 122b: 48 89 e5 mov %rsp,%rbp 122e: 89 7d fc mov %edi,-0x4(%rbp) 1231: 89 75 f8 mov %esi,-0x8(%rbp) 1234: 83 7d f8 00 cmpl $0x0,-0x8(%rbp) 1238: 0f 95 c0 setne %al 123b: 5d pop %rbp 123c: c3 retq 000000000000123d <_Z7compareIdEbT_S0_>: //compare<double>(1.0,2.0); double 类型的函数 123d: f3 0f 1e fa endbr64 1241: 55 push %rbp 1242: 48 89 e5 mov %rsp,%rbp 1245: f2 0f 11 45 f8 movsd %xmm0,-0x8(%rbp) 124a: f2 0f 11 4d f0 movsd %xmm1,-0x10(%rbp) 124f: 66 0f ef c0 pxor %xmm0,%xmm0 1253: 66 0f 2e 45 f0 ucomisd -0x10(%rbp),%xmm0 1258: 0f 9a c0 setp %al 125b: ba 01 00 00 00 mov $0x1,%edx 1260: 66 0f ef c0 pxor %xmm0,%xmm0 1264: 66 0f 2e 45 f0 ucomisd -0x10(%rbp),%xmm0 1269: 0f 45 c2 cmovne %edx,%eax 126c: 5d pop %rbp 126d: c3 retq 126e: 66 90 xchg %ax,%ax0000000000001270 <__libc_csu_init>: 1270: f3 0f 1e fa endbr64 1274: 41 57 push %r15 1276: 4c 8d 3d 13 2b 00 00 lea 0x2b13(%rip),%r15 # 3d90 <__frame_dummy_init_array_entry> 127d: 41 56 push %r14 127f: 49 89 d6 mov %rdx,%r14 1282: 41 55 push %r13 1284: 49 89 f5 mov %rsi,%r13 1287: 41 54 push %r12 1289: 41 89 fc mov %edi,%r12d 128c: 55 push %rbp 128d: 48 8d 2d 0c 2b 00 00 lea 0x2b0c(%rip),%rbp # 3da0 <__do_global_dtors_aux_fini_array_entry> 1294: 53 push %rbx 1295: 4c 29 fd sub %r15,%rbp 1298: 48 83 ec 08 sub $0x8,%rsp 129c: e8 5f fd ff ff callq 1000 <_init> 12a1: 48 c1 fd 03 sar $0x3,%rbp 12a5: 74 1f je 12c6 <__libc_csu_init+0x56> 12a7: 31 db xor %ebx,%ebx 12a9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 12b0: 4c 89 f2 mov %r14,%rdx 12b3: 4c 89 ee mov %r13,%rsi 12b6: 44 89 e7 mov %r12d,%edi 12b9: 41 ff 14 df callq *(%r15,%rbx,8) 12bd: 48 83 c3 01 add $0x1,%rbx 12c1: 48 39 dd cmp %rbx,%rbp 12c4: 75 ea jne 12b0 <__libc_csu_init+0x40> 12c6: 48 83 c4 08 add $0x8,%rsp 12ca: 5b pop %rbx 12cb: 5d pop %rbp 12cc: 41 5c pop %r12 12ce: 41 5d pop %r13 12d0: 41 5e pop %r14 12d2: 41 5f pop %r15 12d4: c3 retq 12d5: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1) 12dc: 00 00 00 00 00000000000012e0 <__libc_csu_fini>: 12e0: f3 0f 1e fa endbr64 12e4: c3 retq Disassembly of section .fini:00000000000012e8 <_fini>: 12e8: f3 0f 1e fa endbr64 12ec: 48 83 ec 08 sub $0x8,%rsp 12f0: 48 83 c4 08 add $0x8,%rsp 12f4: c3 retq

如果compare(100,1.1) // 编译器推演失败 可以 comare(100,1.1);让编译器强转

函数模板是无法编译的，也不进行编译的,函数模板在调用点发生模板实例化动作，被实例化化后 成为模板函数,模板函数才是真正参与编译的

关于模板特例化如果有compare("aaa"，bbb“”); 此时模板会自动推到出如下compare<const char *>(const char * x,const char * y){return x>y;}

上面的比较方式会去比较两个指针地址大小,这种方式不是我们想要的逻辑,所以我们需要根据const char * 写一个特殊的实现方法逻辑如下template<>bool compare<const char *>(const char *x ,const char * y){return strcmp(x,y);}那么上面这个函数就叫做模板的特例化 特例化特殊在不再由编译器自动生成函数，使用自己的实现方式

普通函数和函数模板选择问题 示例代码

点击查看代码如果有//这是个函数模板template<>bool compare<const char *>(const char *x ,const char * y){ return strcmp(x,y);}//这是一个普通的函数bool compare(const char *x ,const char * y){ return strcmp(x,y);}有bool b=compare("aa","bb");//那么编译器会优选能匹配的普通的函数,避免编译器再去生成函数bool b1=compare<const char *>("aa","bb");//这个时候会使用模板特例化//所以我们会遇到 函数模板, 模板特例化, 普通函数都可以匹配调用的时候，如何选择需要知道,自动推演有普通函数能用的,用普通函数,没有普通函数如果有模板特例化的用特例化,没有特例化的,编译器去生成指定类型函数

下面我们看一下模板和调用点分文件编写遇到的问题

只有函数模板,编译后查看符号表情况,点击查看代码// test1.cpp 代码如下#include <iostream>#include <cstring>using namespace std;//这是一个函数模板template<typename T>bool compare(T x,T y){ return x,y;}//test1.cpp 编译后 符号表情况如下,编译后没有 函数符号uos20@uos20-PC:~/Desktop/CPP$ g++ -c test1.cpp -o test1.o -guos20@uos20-PC:~/Desktop/CPP$ objdump -t test1.otest1.o： 文件格式 elf64-x86-64SYMBOL TABLE:0000000000000000 l df *ABS* 0000000000000000 test1.cpp0000000000000000 l d .text 0000000000000000 .text0000000000000000 l d .data 0000000000000000 .data0000000000000000 l d .bss 0000000000000000 .bss0000000000000000 l d .rodata 0000000000000000 .rodata0000000000000000 l O .rodata 0000000000000001 _ZStL19piecewise_construct0000000000000000 l O .bss 0000000000000001 _ZStL8__ioinit0000000000000000 l F .text 000000000000003e _Z41__static_initialization_and_destruction_0ii000000000000003e l F .text 0000000000000015 _GLOBAL__sub_I_test1.cpp0000000000000000 l d .init_array 0000000000000000 .init_array0000000000000000 l d .debug_info 0000000000000000 .debug_info0000000000000000 l d .debug_abbrev 0000000000000000 .debug_abbrev0000000000000000 l d .debug_aranges 0000000000000000 .debug_aranges0000000000000000 l d .debug_line 0000000000000000 .debug_line0000000000000000 l d .debug_str 0000000000000000 .debug_str0000000000000000 l d .note.GNU-stack 0000000000000000 .note.GNU-stack0000000000000000 l d .eh_frame 0000000000000000 .eh_frame0000000000000000 l d .comment 0000000000000000 .comment0000000000000000 *UND* 0000000000000000 _ZNSt8ios_base4InitC1Ev0000000000000000 *UND* 0000000000000000 .hidden __dso_handle0000000000000000 *UND* 0000000000000000 _ZNSt8ios_base4InitD1Ev0000000000000000 *UND* 0000000000000000 __cxa_atexit有函数模板及一个特例化,编译后查看符号表情况,点击查看代码// test1.cpp 代码如下#include <iostream>#include <cstring>using namespace std;//这是一个函数模板template<typename T>bool compare(T x,T y){ return x,y;}//模板特例化template<>bool compare(const char * x, const char * y){ return strcmp(x,y);}//test1.cpp 编译后 符号表情况如下,编译后没有 函数符号uos20@uos20-PC:~/Desktop/CPP$ g++ -c test1.cpp -o test1.o -guos20@uos20-PC:~/Desktop/CPP$ objdump -t test1.otest1.o： 文件格式 elf64-x86-64SYMBOL TABLE:0000000000000000 l df *ABS* 0000000000000000 test1.cpp0000000000000000 l d .text 0000000000000000 .text0000000000000000 l d .data 0000000000000000 .data0000000000000000 l d .bss 0000000000000000 .bss0000000000000000 l d .rodata 0000000000000000 .rodata0000000000000000 l O .rodata 0000000000000001 _ZStL19piecewise_construct0000000000000000 l O .bss 0000000000000001 _ZStL8__ioinit000000000000002a l F .text 000000000000003e _Z41__static_initialization_and_destruction_0ii0000000000000068 l F .text 0000000000000015 _GLOBAL__sub_I__Z7compareIPKcEbT_S2_ // 特例化函数符号compare0000000000000000 l d .init_array 0000000000000000 .init_array0000000000000000 l d .debug_info 0000000000000000 .debug_info0000000000000000 l d .debug_abbrev 0000000000000000 .debug_abbrev0000000000000000 l d .debug_aranges 0000000000000000 .debug_aranges0000000000000000 l d .debug_line 0000000000000000 .debug_line0000000000000000 l d .debug_str 0000000000000000 .debug_str0000000000000000 l d .note.GNU-stack 0000000000000000 .note.GNU-stack0000000000000000 l d .eh_frame 0000000000000000 .eh_frame0000000000000000 l d .comment 0000000000000000 .comment0000000000000000 g F .text 000000000000002a _Z7compareIPKcEbT_S2_0000000000000000 *UND* 0000000000000000 strcmp0000000000000000 *UND* 0000000000000000 _ZNSt8ios_base4InitC1Ev0000000000000000 *UND* 0000000000000000 .hidden __dso_handle0000000000000000 *UND* 0000000000000000 _ZNSt8ios_base4InitD1Ev0000000000000000 *UND* 0000000000000000 __cxa_atexit有函数模板及一个特例化和一个普通函数,编译后查看符号表情况,点击查看代码// test1.cpp 代码如下#include <iostream>#include <cstring>using namespace std;//这是一个函数模板template<typename T>bool compare(T x,T y){ return x,y;}//模板特例化template<>bool compare(const char * x, const char * y){ return strcmp(x,y);}//这是一个普通的函数,不是模板,与模板无关bool compare( const char * x, const char * y){ return x>y;}//编译完成后,我们再符号表中 看到两处 compare ,一处是特例化,一处是 普通compare函数uos20@uos20-PC:~/Desktop/CPP$ g++ -c test1.cpp -o test1.o -guos20@uos20-PC:~/Desktop/CPP$ objdump -t test1.otest1.o： 文件格式 elf64-x86-64SYMBOL TABLE:0000000000000000 l df *ABS* 0000000000000000 test1.cpp0000000000000000 l d .text 0000000000000000 .text0000000000000000 l d .data 0000000000000000 .data0000000000000000 l d .bss 0000000000000000 .bss0000000000000000 l d .rodata 0000000000000000 .rodata0000000000000000 l O .rodata 0000000000000001 _ZStL19piecewise_construct0000000000000000 l O .bss 0000000000000001 _ZStL8__ioinit0000000000000043 l F .text 000000000000003e _Z41__static_initialization_and_destruction_0ii0000000000000081 l F .text 0000000000000015 _GLOBAL__sub_I__Z7compareIPKcEbT_S2_0000000000000000 l d .init_array 0000000000000000 .init_array0000000000000000 l d .debug_info 0000000000000000 .debug_info0000000000000000 l d .debug_abbrev 0000000000000000 .debug_abbrev0000000000000000 l d .debug_aranges 0000000000000000 .debug_aranges0000000000000000 l d .debug_line 0000000000000000 .debug_line0000000000000000 l d .debug_str 0000000000000000 .debug_str0000000000000000 l d .note.GNU-stack 0000000000000000 .note.GNU-stack0000000000000000 l d .eh_frame 0000000000000000 .eh_frame0000000000000000 l d .comment 0000000000000000 .comment0000000000000000 g F .text 000000000000002a _Z7compareIPKcEbT_S2_ //compare 函数符号0000000000000000 *UND* 0000000000000000 strcmp000000000000002a g F .text 0000000000000019 _Z7comparePKcS0_ //compare函数符号0000000000000000 *UND* 0000000000000000 _ZNSt8ios_base4InitC1Ev0000000000000000 *UND* 0000000000000000 .hidden __dso_handle0000000000000000 *UND* 0000000000000000 _ZNSt8ios_base4InitD1Ev0000000000000000 *UND* 0000000000000000 __cxa_atexit分文件编写,测试代码1,点击查看代码// test1.cpp#include <iostream>#include <cstring>using namespace std;//这是一个函数模板template<typename T>bool compare(T x,T y){ return x,y;}//test2.cpp#include <iostream>#include <cstring>using namespace std;template<typename T>bool compare(T x, T y);int main() { bool b1 = compare<int>(1, 2); bool b2 = compare<double>(100.1, 200.1); return 1;}// 编译 报 两处错 //无法解析的外部符号 "bool __cdecl compare<double>(double,double)//无法解析的外部符号 "bool __cdecl compare<int>(int,int)//为什么会出现链接错误？我先看一下test2.cpp编译后的符号表情况 如下uos20@uos20-PC:~/Desktop/CPP$ g++ -c test2.cpp -o test2.o -guos20@uos20-PC:~/Desktop/CPP$ objdump -t test2.otest2.o： 文件格式 elf64-x86-64SYMBOL TABLE:0000000000000000 l df *ABS* 0000000000000000 test2.cpp0000000000000000 l d .text 0000000000000000 .text0000000000000000 l d .data 0000000000000000 .data0000000000000000 l d .bss 0000000000000000 .bss0000000000000000 l d .rodata 0000000000000000 .rodata0000000000000000 l O .rodata 0000000000000001 _ZStL19piecewise_construct0000000000000000 l O .bss 0000000000000001 _ZStL8__ioinit0000000000000039 l F .text 000000000000003e _Z41__static_initialization_and_destruction_0ii0000000000000077 l F .text 0000000000000015 _GLOBAL__sub_I_main0000000000000000 l d .init_array 0000000000000000 .init_array0000000000000000 l d .debug_info 0000000000000000 .debug_info0000000000000000 l d .debug_abbrev 0000000000000000 .debug_abbrev0000000000000000 l d .debug_aranges 0000000000000000 .debug_aranges0000000000000000 l d .debug_line 0000000000000000 .debug_line0000000000000000 l d .debug_str 0000000000000000 .debug_str0000000000000000 l d .note.GNU-stack 0000000000000000 .note.GNU-stack0000000000000000 l d .eh_frame 0000000000000000 .eh_frame0000000000000000 l d .comment 0000000000000000 .comment0000000000000000 g F .text 0000000000000039 main0000000000000000 *UND* 0000000000000000 _Z7compareIiEbT_S0_ //compare<int> 函数符号 UND形式0000000000000000 *UND* 0000000000000000 _Z7compareIdEbT_S0_ //compare<double> 函数符号 UND形式0000000000000000 *UND* 0000000000000000 _ZNSt8ios_base4InitC1Ev0000000000000000 *UND* 0000000000000000 .hidden __dso_handle0000000000000000 *UND* 0000000000000000 _ZNSt8ios_base4InitD1Ev0000000000000000 *UND* 0000000000000000 __cxa_atexit//test2.cpp 和 test1.cpp 分离编译，test2.cpp 有 compare<int>函数符号 UND(外部引用) 和 compare<double>函数符号 UND(外部引用)//然而test1.cpp只是模板 编译时 没有 compare<int>(int a,int b) 和compare<double>(double a, double b)产生编译,//所以链接的时候,test2.o 的 UND函数需要去其他目标文件中找compare<int>(int a, int b)和compare<double>(double a, double b)的定义,找不到,编译报错分文件编写,测试代码2,点击查看代码// test1.cpp#include <iostream>#include <cstring>using namespace std;//这是一个函数模板template<typename T>bool compare(T x,T y){ return x,y;}//模板特例化template<>bool compare<const char *>(const char * x, const char * y) {return strcmp(x, y);}//test2.cpp#include <iostream>#include <cstring>using namespace std;template<typename T>bool compare(T x, T y);int main() { bool b3 = compare("aaa", "bbb"); return 1;}//正常编译通过并调用分文件编写,测试代码3 ,点击查看代码//test1.cpp#include <iostream>#include <cstring>using namespace std;//这是一个函数模板template<typename T>bool compare(T x, T y) {return x, y;}//模板特例化template<>bool compare<const char *>(const char * x, const char * y) {cout << "Template Function" << endl;return strcmp(x, y);}//这是一个普通的函数,不是模板,与模板无关bool compare(const char * x, const char * y) {cout << "Normal Function" << endl;return x>y;}//test2.cpp#include <iostream>#include <cstring>using namespace std;template<typename T>bool compare(T x, T y);bool compare(const char * x, const char * y);int main() { bool b3 = compare("aaa", "bbb"); return 1;}//正常编译通过,调用普通函数分文件编写,测试代码4,点击查看代码// test1.cpp#include <iostream>#include <cstring>using namespace std;//这是一个函数模板template<typename T>bool compare(T x, T y) {return x, y;}//模板特例化template<>bool compare<const char *>(const char * x, const char * y) {cout << "Template Function" << endl;return strcmp(x, y);}//这是一个普通的函数,不是模板,与模板无关bool compare(const char * x, const char * y) {cout << "Normal Function" << endl;return x>y;}//编译后, .o文件中有两处 compare函数符号,一处是 普通函数的,一处是 模板特例化函数的// test2.cpp 情况1 下面test2.cpp编译后，.o文件中没有compare函数符号#include <iostream>#include <cstring>using namespace std;//模板