在Mac OS 15.5系统中，最近想用C++23，试了试gcc15.2，发现出现无法链接模块功能：
首先下一个最简单的Helloworld.cpp:
import std;
int main()
{
std::println("Hello,world!");
return 0;
}
使用gcc15.2编译:
g++-15 -std=c++23 -fmodules helloworld.cpp
出现链接不到模块的错误:
Undefined symbols for architecture arm64:
"initializer for module std", referenced from:
__static_initialization_and_destruction_0() in ccEgD1TM.o
ld: symbol(s) not found for architecture arm64
collect2: error: ld returned 1 exit status
参考了网上一位大神的文章介绍：https://download.csdn.net/blog/column/11938572/149222276
使用这个命令重新编译：g++ -std=c++23 -fmodules -fsearch-include-path bits/std.cc helloworld.cpp
bit/std.cc是std模块所在位置，我们需要找出gcc15.2在Mac OS中安装位置，使用这个命令可以找到：g++-15 -print-search-dirs
gcc15.2安装位置:
install: /opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/aarch64-apple-darwin24/15/
programs: =/opt/homebrew/Cellar/gcc/15.2.0/bin/../libexec/gcc/aarch64-apple-darwin24/15/:/opt/homebrew/Cellar/gcc/15.2.0/bin/../libexec/gcc/:/opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/aarch64-apple-darwin24/15/../../../../../../aarch64-apple-darwin24/bin/aarch64-apple-darwin24/15/:/opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/aarch64-apple-darwin24/15/../../../../../../aarch64-apple-darwin24/bin/
libraries: =/opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/aarch64-apple-darwin24/15/:/opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/:/opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/aarch64-apple-darwin24/15/../../../../../../aarch64-apple-darwin24/lib/aarch64-apple-darwin24/15/:/opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/aarch64-apple-darwin24/15/../../../../../../aarch64-apple-darwin24/lib/:/opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/aarch64-apple-darwin24/15/../../../aarch64-apple-darwin24/15/:/opt/homebrew/Cellar/gcc/15.2.0/bin/../lib/gcc/current/gcc/aarch64-apple-darwin24/15/../../../
可以看到std.cc模块位置是: /opt/homebrew/Cellar/gcc/15.2.0/include/c++/15/bits/std.cc
然后替换一下刚才的编译命令中std.cc的位置即可:
g++-15 -std=c++23 -fmodules -fsearch-include-path /opt/homebrew/Cellar/gcc/15.2.0/include/c++/15/bits/std.cc helloworld.cpp
./a.out
Hello,world!
大功告成，希望C++23成熟以后，不用自己手动指定模块位置吧。