每次尝试使用‘`clang -Weverything`’编译时，收到警告“包括位置”/usr/local/include‘对于交叉编译都是不安全的。

Question

很抱歉，如果这个问题不清楚，我甚至很难开始调试这个问题。我在macOS上，每次使用clang使用-Weverything and -Werror标志编译C程序时，我都会收到以下错误/警告：

error: include location '/usr/local/include' is unsafe for cross-compilation [-Werror,-Wpoison-system-directories]

起初，我认为这是一个与我的代码相关的问题，但我发现，这个错误现在发生在我试图编译的每个程序中。尽管总是使用这些标志进行编译，但我以前从未犯过这样的错误，因为现在每个程序都会发生这种错误，我怀疑这是我的编译器或系统改变了的东西。最近我唯一能想到的改变就是我用VirtualBox上的Lubuntu制作了几个共享文件夹，并更新了Xcode。

我可以在不使用-Weverything标志的情况下编译程序，它看起来像预期的那样工作，但是我想解决继续使用-Weverything的实际问题。正如其他人以及这个线程here所提到的，在现实生活中使用-Weverything -Werror是过度的，然而，我主要是将它用作学习工具，我想了解为什么这个问题甚至出现在helloworld.c这样的基本程序中(见下文)。

我遇到了一个讨论here，但是答案引用了一个我不熟悉并且不知道如何使用的configure.ac文件。

如果我能提供更多的信息来帮助调试这个问题，请告诉我。

举个例子，下面是cc -Weverything -Werror -v helloworld.c的结果

Apple clang version 12.0.0 (clang-1200.0.32.2)
Target: x86_64-apple-darwin19.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.15.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -Werror=implicit-function-declaration -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name helloworld.c -mrelocation-model pic -pic-level 2 -mthread-model posix -mframe-pointer=all -fno-strict-return -masm-verbose -munwind-tables -target-sdk-version=10.15.6 -fcompatibility-qualified-id-block-type-checking -target-cpu penryn -dwarf-column-info -debugger-tuning=lldb -target-linker-version 609 -v -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/12.0.0 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -I/usr/local/include -internal-isystem /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/local/include -internal-isystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/12.0.0/include -internal-externc-isystem /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include -internal-externc-isystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include -Weverything -Werror -Wno-reorder-init-list -Wno-implicit-int-float-conversion -Wno-c99-designator -Wno-final-dtor-non-final-class -Wno-extra-semi-stmt -Wno-misleading-indentation -Wno-quoted-include-in-framework-header -Wno-implicit-fallthrough -Wno-enum-enum-conversion -Wno-enum-float-conversion -fdebug-compilation-dir /Users/Projects/helloworld -ferror-limit 19 -fmessage-length 204 -stack-protector 1 -fstack-check -mdarwin-stkchk-strong-link -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fgnuc-version=4.2.1 -fobjc-runtime=macosx-10.15.0 -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/mn/v00y5wf55qjf76r4q9rvxq1c0000gn/T/helloworld-89fdc3.o -x c helloworld.c
clang -cc1 version 12.0.0 (clang-1200.0.32.2) default target x86_64-apple-darwin19.6.0
error: include location '/usr/local/include' is unsafe for cross-compilation [-Werror,-Wpoison-system-directories]
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/local/include"
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/12.0.0/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks (framework directory)
End of search list.
1 error generated.

Answer 1

您有两个选项可以消除此警告。

1. 使用-Wno-poison-system-directories选项.

忽略此警告。

请注意，使用-Wno-作为前缀适用于所有警告。

全员指挥：

cc -Weverything -Wno-poison-system-directories -Werror helloworld.c

1. 使用-isysroot选项.

设置逻辑系统根。

完整命令(如果安装了开发人员命令行工具)：

cc -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -Weverything -Werror helloworld.c

Full命令(从Xcode内部使用SDK )：

cc -isysroot "$(xcode-select --print-path)/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk" -Weverything -Werror helloworld.c