[clang] [clang][Driver] Fix libc++ include path on FreeBSD (PR #212725)

[Rainer Orth via cfe-commits]

https://github.com/rorth created https://github.com/llvm/llvm-project/pull/212725

`clang++` defaults to `-stdlib=libc++` on FreeBSD.  When building with both `clang` and `libcxx` included, the freshly built `clang++` uses the system version of the `libc++` headers.  However, this is from the bundled `libc++` 19.1.7, thus inconsistent with the `libc++` being built.

Similarly to the NetBSD case, FreeBSD has its own version of `addLibCxxIncludePaths` which just includes `/usr/include/c++/v1`.

Rather than replicating the generic version in `Gnu.cpp`, this patch just calls `Generic_GCC::addLibCxxIncludePaths`.

Tested on `amd64-pc-freebsd15.1`.

This breaks the `Driver/freebsd.cpp` and `Driver/freebsd-include-paths.c` testcases.  Once it can be confirmed the approach is sound, I'll  update them accordingly.

>From 6c1e69756696c56672c678a111fdb5b0f4bd2005 Mon Sep 17 00:00:00 2001
From: Rainer Orth <ro at gcc.gnu.org>
Date: Wed, 29 Jul 2026 11:27:31 +0200
Subject: [PATCH] [clang][Driver] Fix libc++ include path on FreeBSD

`clang++` defaults to `-stdlib=libc++` on FreeBSD.  When building with both
`clang` and `libcxx` included, the freshly built `clang++` uses the system
version of the `libc++` headers.  However, this is from the bundled
`libc++` 19.1.7, thus inconsistent with the `libc++` being built.

Similarly to the NetBSD case, FreeBSD has its own version of
addLibCxxIncludePaths which just includes `/usr/include/c++/v1`.

Rather than replicating the generic version in `Gnu.cpp`, this patch just
calls `Generic_GCC::addLibCxxIncludePaths`.

Tested on `amd64-pc-freebsd15.1`.

This breaks the `Driver/freebsd.cpp` and `Driver/freebsd-include-paths.c`
testcases.  Once it can be confirmed the approach is sound, I'll  update
them accordingly.
---
 clang/lib/Driver/ToolChains/FreeBSD.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/FreeBSD.cpp b/clang/lib/Driver/ToolChains/FreeBSD.cpp
index 724ccbefd790f..519999a9a5bcf 100644
--- a/clang/lib/Driver/ToolChains/FreeBSD.cpp
+++ b/clang/lib/Driver/ToolChains/FreeBSD.cpp
@@ -10,6 +10,7 @@
 #include "Arch/ARM.h"
 #include "Arch/Mips.h"
 #include "Arch/Sparc.h"
+#include "Gnu.h"
 #include "clang/Config/config.h"
 #include "clang/Driver/CommonArgs.h"
 #include "clang/Driver/Compilation.h"
@@ -434,8 +435,7 @@ void FreeBSD::AddClangSystemIncludeArgs(
 
 void FreeBSD::addLibCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
                                     llvm::opt::ArgStringList &CC1Args) const {
-  addSystemInclude(DriverArgs, CC1Args,
-                   concat(getDriver().SysRoot, "/usr/include/c++/v1"));
+  Generic_GCC::addLibCxxIncludePaths(DriverArgs, CC1Args);
 }
 
 void FreeBSD::AddCXXStdlibLibArgs(const ArgList &Args,