clang does not support long paths

[fekir]

Bugzilla Link	47622
Version	trunk
OS	Windows NT
CC	@zygoloid

Extended Description

Hello, clang is inconsistent on how ti handles long paths.

I'm using the cygwin environment for simplicity, but it has nothing to do with cygwin, as it is only used for calling clang and creating feils/directories.

---

LONG_DIR="D:/1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234/12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890/12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"
mkdir -p "$LONG_DIR"
echo "int main(){}" > "$LONG_DIR/main.cpp"
'/cygdrive/c/Program Files/LLVM/bin/clang++.exe' "$LONG_DIR/main.cpp" -o "$LONG_DIR/main.exe"

LINK : fatal error LNK1104: cannot open file 'D:\1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234\12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890\123456789012345678901234567890123456789012345
67890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890\main.exe'

While following works without issues

---

LONG_DIR="D:/1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234/12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890/12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"
mkdir -p "$LONG_DIR"
echo "int main(){}" > "$LONG_DIR/main.cpp"
'/cygdrive/c/Program Files/LLVM/bin/clang++.exe' "$LONG_DIR/main.cpp"

Thus it seems that clang has issues writing, not reading, files in long paths.

If case it is relevant, I've enabled "LongPathsEnabled" on my machine (Windows 10 Version 1909).

[fekir]

Also note that using

LONG_DIR='\?\D:\1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234\12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890\12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890'

as path did not change anything, the inconsistency is still there.

[bgamari]

#54559 notes a similar issue in llvm-ar.

[RyanGlScott]

I think this issue may be fixed as of Clang 14.0.6. Here is a standalone script:

#!/usr/bin/env bash

DIR="aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
LONG_DIR="$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR/$DIR"
mkdir -p "$LONG_DIR"
echo "int main(){}" > "$LONG_DIR/main.cpp"
clang++.exe --version
clang++.exe "$LONG_DIR/main.cpp" -o "$LONG_DIR/main.exe" && echo "Long path used successfully"

If I use Clang 13.0.0, then this fails:

$ PATH=/c/ghcup/ghc/9.4.1/mingw/bin:$PATH ./test.sh
clang version 13.0.0
Target: x86_64-w64-windows-gnu
Thread model: posix
InstalledDir: C:/ghcup/ghc/9.4.1/mingw/bin
clang++: error: no such file or directory: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/main.cpp'
clang++: error: no input files

If I use Clang 14.0.6, however, then this succeeds:

$ ./test.sh
clang version 14.0.6
Target: x86_64-w64-windows-gnu
Thread model: posix
InstalledDir: C:/msys64/clang64/bin
Long path used successfully

[mplatings]

Yes, this works for me also. https://reviews.llvm.org/D75372 looks like the fix, but that predates this issue so maybe it was https://reviews.llvm.org/D111880. Closing.