如何避免gcc搜索路径中多版本Boost引发的编译问题？

问题背景 #

共享集群环境下，主目录自行部署了gcc 12.1.0和Boost 1.81.0，但集群/usr/local/include目录存在旧版Boost 1.66。编译依赖Boost的程序时，GCC有时会优先加载旧版头文件，引发编译错误。

添加-I/home/charlesprior/include参数后，GCC头文件搜索列表如下：

GNU C++23 (GCC) version 12.1.0 (x86_64-pc-linux-gnu)
    compiled by GNU C version 12.1.0, GMP version 6.2.1, MPFR version 4.1.0, MPC version 1.2.1, isl version none
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/home/charlesprior/lib/gcc/x86_64-pc-linux-gnu/12.1.0/../../../../x86_64-pc-linux-gnu/include"
ignoring duplicate directory "/home/charlesprior/include"
  as it is a non-system directory that duplicates a system directory
#include "..." search starts here:
#include <...> search starts here:
 /home/charlesprior/lib/gcc/x86_64-pc-linux-gnu/12.1.0/../../../../include/c++/12.1.0
 /home/charlesprior/lib/gcc/x86_64-pc-linux-gnu/12.1.0/../../../../include/c++/12.1.0/x86_64-pc-linux-gnu
 /home/charlesprior/lib/gcc/x86_64-pc-linux-gnu/12.1.0/../../../../include/c++/12.1.0/backward
 /home/charlesprior/lib/gcc/x86_64-pc-linux-gnu/12.1.0/include
 /usr/local/include
 /home/charlesprior/include
 /home/charlesprior/lib/gcc/x86_64-pc-linux-gnu/12.1.0/include-fixed
 /usr/include
End of search list.

可见/usr/local/include排在/home/charlesprior/include之前，且手动添加-I参数被判定为重复目录而忽略。

编译错误示例 #

In file included from /home/charlesprior/include/boost/histogram/detail/detect.hpp:11,
                 from /home/charlesprior/include/boost/histogram/axis/traits.hpp:12,
                 from /home/charlesprior/include/boost/histogram/indexed.hpp:12,
                 from /home/charlesprior/include/boost/histogram/algorithm/empty.hpp:11,
                 from /home/charlesprior/include/boost/histogram/algorithm.hpp:15,
                 from /home/charlesprior/include/boost/histogram.hpp:27,
                 from test.cpp:1:
/usr/local/include/boost/mp11/function.hpp: In substitution of ‘template<class ... T> using variant_ca_base = boost::variant2::detail::variant
_ca_base_impl<std::integral_constant<bool, (static_cast<bool>(std::is_copy_constructible<T>::value) ... && static_cast<bool>(std::is_copy_assignable<T>::value) ...)>::value, std::integral_constant<bool, (static_cast<bool>(std::is_trivially_destructible<T>::value) ... && (static_cast<bool>(std::is_trivially_copy_constructible<T>::value) ... && static_cast<bool>(std::is_trivially_copy_assignable<T>::value) ...))>::value, T ...> [with T = {T ...}]’:
/home/charlesprior/include/boost/variant2/variant.hpp:1449:96:   required from here
/usr/local/include/boost/mp11/function.hpp:97:77: error: invalid use of pack expansion expression

错误根源是GCC加载了/usr/local/include中的旧版Boost头文件。

解决方案 #

1. 通过环境变量调整搜索优先级 #

设置CPLUS_INCLUDE_PATH环境变量，将主目录include放在最前面，让GCC优先搜索：

export CPLUS_INCLUDE_PATH="/home/charlesprior/include:$CPLUS_INCLUDE_PATH"

若要永久生效，可将该命令添加到~/.bashrc或~/.profile中。

2. 使用-isystem标记目录为系统路径 #

编译时用-isystem替代-I，将主目录include标记为系统目录并置于默认系统路径之前：

g++ -isystem /home/charlesprior/include test.cpp -o test

此方法会让GCC优先搜索该目录，且不会触发重复目录的警告。

3. 设置编译别名简化操作 #

若不想每次编译都手动添加参数，可设置g++别名：

alias g++='g++ -isystem /home/charlesprior/include'

同样可将别名添加到~/.bashrc中永久生效。

内容的提问来源于stack exchange，提问作者Charlie