本文指在帮助需要的朋友理解链接的使用
环境准备
源文件 main.c
#include <stdio.h>
int main()
{
printf("Hello World from t1 Main!\n");
return 0;
}
编译文件
gcc -v main.c
生成a.out文件执行
编译日志为：
Apple LLVM version 10.0.1 (clang-1001.0.46.4)
Target: x86_64-apple-darwin18.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
"/Library/Developer/CommandLineTools/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.14.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name main.c -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -fno-strict-return -masm-verbose -munwind-tables -target-sdk-version=10.14 -target-cpu penryn -dwarf-column-info -debugger-tuning=lldb -target-linker-version 450.3 -v -resource-dir /Library/Developer/CommandLineTools/usr/lib/clang/10.0.1 -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -I/usr/local/include -Wno-atomic-implicit-seq-cst -Wno-framework-include-private-from-public -Wno-atimport-in-framework-header -Wno-quoted-include-in-framework-header -fdebug-compilation-dir /Users/wangshengxing/project/c/gcc/ld/src -ferror-limit 19 -fmessage-length 159 -stack-protector 1 -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fobjc-runtime=macosx-10.14.0 -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/d0/z0p0y29541n_z25rrkc8c5xw0000gn/T/main-377173.o -x c main.c
clang -cc1 version 10.0.1 (clang-1001.0.46.4) default target x86_64-apple-darwin18.6.0
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/local/include"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/Library/Developer/CommandLineTools/usr/lib/clang/10.0.1/include
/Library/Developer/CommandLineTools/usr/include
/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include
/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/System/Library/Frameworks (framework directory)
End of search list.
"/Library/Developer/CommandLineTools/usr/bin/ld" -demangle -lto_library /Library/Developer/CommandLineTools/usr/lib/libLTO.dylib -no_deduplicate -dynamic -arch x86_64 -macosx_version_min 10.14.0 -syslibroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -o a.out /var/folders/d0/z0p0y29541n_z25rrkc8c5xw0000gn/T/main-377173.o -L/usr/local/lib -lSystem /Library/Developer/CommandLineTools/usr/lib/clang/10.0.1/lib/darwin/libclang_rt.osx.a
连接文件
编译文件
执行
gcc main.c
输出 main.o文件
初步连接
执行
ld main.o -o hello
输出
ld: warning: No version-min specified on command line
Undefined symbols for architecture x86_64:
"_printf", referenced from:
_main in main.o
ld: symbol(s) not found for inferred architecture x86_64
没有找到引用，说明没有找到链接库：
查看链接库
执行:
otool -L a.out
输出：
说明需要连接System库
加入System库
执行
ld -o hello main.o -L/usr/local/lib -lSystem
输出
说明已经链接成功
详细参数说明
版本1
ld -arch x86_64 -macosx_version_min 10.14.0 -o hello main.o -L/usr/local/lib -lSystem
版本2
ld -demangle -lto_library /Library/Developer/CommandLineTools/usr/lib/libLTO.dylib -no_deduplicate -dynamic -arch x86_64 -macosx_version_min 10.14.0 -syslibroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -o hello main.o -L/usr/local/lib -lSystem /Library/Developer/CommandLineTools/usr/lib/clang/10.0.1/lib/darwin/libclang_rt.osx.a