<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/66704>66704</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
Bug in getInstalledDir() prevents picking up the correct headers when clang is started via a link
</td>
</tr>
<tr>
<th>Labels</th>
<td>
clang
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
ilg-ul
</td>
</tr>
</table>
<pre>
In `clang/tools/driver/driver.cpp`, the function `SetInstallDir()` tries to determine the location where the toolchain is installed, basically by taking the parent folder of the executable absolute path:
https://github.com/llvm/llvm-project/blob/9bbec0ad42a8e8c8f564a36adb1e819a0921a7f9/clang/tools/driver/driver.cpp#L344
This works for regular use cases, but fails if the executable is started via a soft link, when this code returns the parent of the link, not the parent of the executable after following the link(s).
This case is specific to the npm/xpm ecosystem, where multi-version dependencies are managed by creating soft links into a local `.bin` folder instead of adding lots of folders to the `PATH`.
Below is a functional example of a simple compile step on macOS, when the compiler is invoked with the absolute path:
```console
% /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/bin/clang++ -v hello.cpp -stdlib=libc++
xPack x86_64 clang version 15.0.7 (https://github.com/xpack-dev-tools/clang-xpack 9b1ff65945b1aaddfe7c0c4d99001ebca5d67b03)
Target: x86_64-apple-darwin21.6.0
Thread model: posix
InstalledDir: /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/bin <-- Correct!
"/Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/bin/clang-15" -cc1 -triple x86_64-apple-macosx12.0.0 -Wundef-prefix=TARGET_OS_ -Werror=undef-prefix -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all --mrelax-relocations -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name hello.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=all -ffp-contract=on -fno-rounding-math -funwind-tables=2 -fcompatibility-qualified-id-block-type-checking -fvisibility-inlines-hidden-static-local-var -target-cpu penryn -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=lldb -target-linker-version 409.12 -v -fcoverage-compilation-dir=/Users/ilg/tmp -resource-dir /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/clang/15.0.7 -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -stdlib=libc++ -internal-isystem /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/bin/../include/c++/v1 -internal-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/local/include -internal-isystem /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/clang/15.0.7/include -internal-externc-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include -fdeprecated-macro -fdebug-compilation-dir=/Users/ilg/tmp -ferror-limit 19 -stack-protector 1 -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fmax-type-align=16 -fcolor-diagnostics -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /var/folders/gr/13tt3vcd7m1gnbhwtkmf5cnw0000gn/T/hello-1fa361.o -x c++ hello.cpp
clang -cc1 version 15.0.7 based upon LLVM 15.0.7 default target x86_64-apple-darwin21.6.0
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/local/include"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
/Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/bin/../include/c++/v1 <-- Correct
/Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/clang/15.0.7/include
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks (framework directory)
End of search list.
"/usr/bin/ld" -demangle -lto_library /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/libLTO.dylib -no_deduplicate -dynamic -arch x86_64 -macosx_version_min 12.0.0 -syslibroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -o a.out /var/folders/gr/13tt3vcd7m1gnbhwtkmf5cnw0000gn/T/hello-1fa361.o -lc++ -lSystem /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/clang/15.0.7/lib/darwin/libclang_rt.osx.a
```
As it can be seen, the correct headers in `.content/bin/../include/c++/v1` were included.
When the compiler is invoked via a link, it computes an invalid `InstalledDir`, then complains about the missing C++ headers folder and finally silently picks the wrong system headers:
```console
% ln -s /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/bin/clang++ ~/tmp/clang++
% ~/tmp/clang++ -v hello.cpp -stdlib=libc++
xPack x86_64 clang version 15.0.7 (https://github.com/xpack-dev-tools/clang-xpack 9b1ff65945b1aaddfe7c0c4d99001ebca5d67b03)
Target: x86_64-apple-darwin21.6.0
Thread model: posix
InstalledDir: /Users/ilg/tmp/. <--- Incorrect!
ignoring nonexistent directory "/Users/ilg/tmp/./../include/c++/v1" <--- Bad!
"/Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/bin/clang-15" -cc1 -triple x86_64-apple-macosx12.0.0 -Wundef-prefix=TARGET_OS_ -Werror=undef-prefix -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all --mrelax-relocations -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name hello.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=all -ffp-contract=on -fno-rounding-math -funwind-tables=2 -fcompatibility-qualified-id-block-type-checking -fvisibility-inlines-hidden-static-local-var -target-cpu penryn -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=lldb -target-linker-version 409.12 -v -fcoverage-compilation-dir=/Users/ilg/tmp -resource-dir /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/clang/15.0.7 -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -stdlib=libc++ -internal-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1 -internal-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/local/include -internal-isystem /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/clang/15.0.7/include -internal-externc-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include -fdeprecated-macro -fdebug-compilation-dir=/Users/ilg/tmp -ferror-limit 19 -stack-protector 1 -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fmax-type-align=16 -fcolor-diagnostics -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /var/folders/gr/13tt3vcd7m1gnbhwtkmf5cnw0000gn/T/hello-a87934.o -x c++ hello.cpp
clang -cc1 version 15.0.7 based upon LLVM 15.0.7 default target x86_64-apple-darwin21.6.0
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/local/include"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1 <--- Wrong!
/Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/clang/15.0.7/include
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks (framework directory)
End of search list.
"/usr/bin/ld" -demangle -lto_library /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/libLTO.dylib -no_deduplicate -dynamic -arch x86_64 -macosx_version_min 12.0.0 -syslibroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -o a.out /var/folders/gr/13tt3vcd7m1gnbhwtkmf5cnw0000gn/T/hello-a87934.o -lc++ -lSystem /Users/ilg/Library/xPacks/@xpack-dev-tools/clang/15.0.7-3.1/.content/lib/clang/15.0.7/lib/darwin/libclang_rt.osx.a
```
Using the system headers instead of the toolchain headers may have very subtle consequences, sometimes leading to compile errors which are hard to diagnose.
The correct implementation of `SetInstallDir()` is platform specific, and requires invoking some system calls, like `proc_pidpath()` on macOS.
In the [xPack LLVM clang](https://github.com/xpack-dev-tools/clang-xpack/) binary distribution I patched `driver.cpp` and fixed the problem.
Attached is the small [patch](https://github.com/llvm/llvm-project/files/12653631/llvm-project.git-566e100-driver.cpp.get.absolute.path.in.SetInstallDir.patch).
If you are interrested, I can try to submit it as a pull request.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzsWl9z27ay_zT0yw44JCjJ1oMfbCtqMzeddpq0uW8aEFhSqEGABUD9ebmf_c6Ckiwlvkl6T5LO6fFMxhHBBfcPdhe7v1kRgm4t4m02vc-miysxxLXzt9q0bDBXtVP729cWslkhjbBtxpfRORMyvlReb9CffuSy77NZkfEHiGuEZrAyapd2vsX42oYojFlon_GbjM-zWQHRawwQHSiM6DttMe00Toq0c7tGPy4RS7kW2oIOoMdPoSJWtQhaCmP2UO8hikdt27SjFx5thMYZhR5ckxZxh3KIojYIog7ODJEI4zqr7rJikRWHv-sY-0BrfJnxZavjeqhz6bqML43ZHP9jvXd_oIwZX9bG1RlfzusaZSHUhIsbvJE3zXQ2EdVMqLrEm3IuijkvxXUzz_jyS2zJqzfVZHIu2Lu1DrB1_jFA4zx4bAcjPAwBQYqAIRlkiNAIbQLoj5TWAUIUPqKCjRYgILgmgtH2kXZu12ghEgvpFILHOHgbzq15MONxg3XxmbfnRm4iejoD47bHgxk334SMz_OPdCMtkpQ9St1oSc5Bm2xPVt_1HaB0YR8idgeJPUI3mKjZBn0gp1HYo1VoJfmWoNfCihYV-Yf0KCIJctKbvCk6EMnpDPlqXmtLznnwHHI2FIqUE0rRXuNioMeRIBxFzGbFL3fvfqQvnKt1j8ZtSSVxighhAHei6w2mr0LQ6bd0Xa8NQojYg7PQCfnz27NzOVH4MQg27hEVbHVcp5efcmgKy_RPOhucwcMqn0LGl78F9OSC2pBDvtG1F35P1v5FyEd6kU2KXS_kI1O4YUeHPTpwOc2L_JpVeZnxZS6djWhTSGj7RHWf8XtgG1ijMY58G1iIyug6qxZG13KkGKVKbGF3M1vNJpD2w_FoR16Q8ZtPROj_ISpL6zCvy6aZTeeTaV0KoVSD17KQEzWfF0WJtRRTNbuui4oy1OiWwrcYs-ruIBITfW-QKeG32vIyn-XF0X89-UnnFBoi713Qu_NDeH1MW5QDq7tvanrIqgfG4MF5nzJUeS4IZJx_j3Nn5TTjHJiUJbDoNTn5hRE7IV3YlTwv8gLY-8EqbFjvsdG7rFq8u_v1h1fvVj-_XQF7j947n1WLcxpg7xX2HqWIqJir_5BMB8GGIFo82_IJGux0pEVgnUcjdkwYA-z44PF4EwVgSgdKaazxiMCkQeGZCJHV2DiPrBbyEa16oks3xAa9bjT6tCyFV2wjzIDMig4DsE5oyxptxoXz6OieeLPkUdBrCazXkhncoAEOrGu86JD1TtuIpGgSvml6RqfhhYxZtXAWWGMd826wlL1YJ-IaWDPYrbaKpTQdsmrBgTWUXkTUtTY67tmfgzAkvGJasdo4-cjivkcm1yjTLcuajQ5Ham2NthjYWiuFloUoIslKSZVthAcWUxwx2Q_Qo_V7CywOFtNCixY96deR1chXUEQWpDCjyfUOFUvHyURgW-Ft4q-wHtoWPX1I25ZyiVH1iRWld_Sne2FSzPOSUxYiTTfoRYtszKijnRWF5eKjwIhdD8xjcIOXSETfLnApIX5IBUyHffDORbjgtCA3cH2qGR5c1wmr3miL7w6s3i7-i_77ie6Q_86Denw24wJLvmOFSVwidt_6Qshz-rCVZlBImw6Zny835fPC_P81zvhyCEScvPCJ7fdU-rkTfVYS3NEP-ZU1P_FpzpJgJ6R3aake2i-OgGaMP6M7HaGckzuRMXrvIsroPJTAmpQmAhFbKiGTVlbhMX9QnyHi4Ekgj60OET1rjauFYSo6HxhVM0xE3OkIrGntII_xm1WLSc5z4iJ3O4Y7if0hNTcXD53YjYlKGN3StnKWIt44z5QWrXUhahmALVarHx4eVj_e_f5qtXh_9-uSrx6Wr1d3b3-iTcAcHcJGkB0PpR6VGvRYVjFWG6muu7K19XobH7tmKu22KIqiJS9_l_FlyuasbEQ1K3MHbAfHoDvl-fE6HmucdEt-UOjUIqCCoXcW3rz5_afjssJGDCbCmOc-V5fo1jpP-dI6izuyuY2gtE-ntj_UAl8_yui734n_0-Yl3YipPzqxz3h1jIKM85zyD4eAwsv12AsFoCbiqWA-o68eiL569Un6Y0n1t6XNy1Lvuwj16bT2xP3rpbCv9M23h9bxWZ-hxqI5Pj256KkVeGVTG3hwBqNDzC8K6lHg8cCMSqWvwk7Y1iAwE93KjEy_9bkYXb9593Ou9kbXwKxbKVRDbzSlf2Bqb0VHxVbS4tBnHUrx1SEBrTpt4ViXh30gwb9CBeJA5G6IXzevmlMtY97-Pbf5uDxm3vExkax8zF3Y5eKDHvw8RO8C6AhSWKgRAqI9omdyDGdYo0ggg0442l_JC9msgC16hMNrdQFLjH_ffwpZGBGiI9ZDYrquHyIGEJaIhNGKhLroa0_4n03kRmgbQNR06sSn0yHQXfBwugpH9Q5gi7AKGm0TnBe0QRvNnjqfxxGF2npnWzhUSIetHyIdn8E7jAUWvifq8T9jAXW5-iTP8-9fsJLPYSWjyfLx8mPw2soPoI4vKjue_eZnworzI9N7oV6QlRdk5QVZeUFWvhBZ-Yr18At28oKd_MOxE3FzPa8mL9jJfwB28u0S46FWe0-tw8fV2gs-8oKP_CPxkafc-W-Nj_wWjmMjl13_-VjG5XzQkaATe1iLDdK9sIcw1DGNWNiAfw5o5TgrE1yHUVPHYFCk4Y7oTnMY6dIOsF1ruU6DJGvhVZpWGm9C_GB85Qm0SfMcHdo4jjG55hMzUDpAb0RsnO9OUy8kmrAKPP45aI8HSGacW-lOppDCmKSF0Y9p_KT3Tq56rdIAyInBcZIkv-yvx5mV6f0IIaQrcjy46eJfwAwS_RxqbSmOlQ7R63pIVngNvYhyjQkzupgYO8A-O1TjNJF3tcHuQt67GEXaq0ckKHTUkmXT-_TNz8r8_NQW9Yckf8ln02pWlR9Q5K2ObDqbYVkU7EngvMWYH4dtcrJ1rm1-cbr5KBWf53Bh9Ab2bkiulGpXjyGOQ2yvEwQY_Z7cKww11Yk6ggggoB-MSZ6Ap3w6_r1St5WaV3NxhbflbD4tris-4Vfr2zmv59MbnFdyWpWT2WzeFFzx-aRUtZxxObnSt7zgVTEvb3g5KSY8RzVXCm_EtZo0jZhjNimwE9rkZI_c-fZKhzDg7Wx2XUyujKjRhDQuyPkh2nk2XVz522S_emhDNinoAghPX4g6Gry9H1rQFtqTuUaIJ3kr9B43aGNIkB-5-9A_C4amgaix9Ptooo16U7gavLn9y_6QdCSHSGr-bwAAAP__kE55cQ">