Support: Do not check if a file exists before executing

[arsenm]

Let the actual syscall error if the file doesn't exist. This produces
a more standard "no such file or directory" phrasing of the error message,
and avoids an extra step.

The same antipattern appears in the windows code, we should probably
fix that one too.

[arsenm]

• Support: Do not check if a file exists before executing #128821 👈 (View in Graphite)
• main

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[llvmbot]

@llvm/pr-subscribers-llvm-support

Author: Matt Arsenault (arsenm)

Changes

Let the actual syscall error if the file doesn't exist. This produces
a more standard "no such file or directory" phrasing of the error message,
and avoids an extra step.

The same antipattern appears in the windows code, we should probably
fix that one too.

---

Full diff: https://github.com/llvm/llvm-project/pull/128821.diff

2 Files Affected:

• (modified) llvm/lib/Support/Unix/Program.inc (-7)
• (modified) llvm/test/tools/llvm-rc/windres-preproc.test (+1-1)

diff --git a/llvm/lib/Support/Unix/Program.inc b/llvm/lib/Support/Unix/Program.inc
index 0708df1eed0a3..6d68369ad191c 100644
--- a/llvm/lib/Support/Unix/Program.inc
+++ b/llvm/lib/Support/Unix/Program.inc
@@ -168,13 +168,6 @@ static bool Execute(ProcessInfo &PI, StringRef Program,
                     ArrayRef<std::optional<StringRef>> Redirects,
                     unsigned MemoryLimit, std::string *ErrMsg,
                     BitVector *AffinityMask, bool DetachProcess) {
-  if (!llvm::sys::fs::exists(Program)) {
-    if (ErrMsg)
-      *ErrMsg = std::string("Executable \"") + Program.str() +
-                std::string("\" doesn't exist!");
-    return false;
-  }
-
   assert(!AffinityMask && "Starting a process with an affinity mask is "
                           "currently not supported on Unix!");
 
diff --git a/llvm/test/tools/llvm-rc/windres-preproc.test b/llvm/test/tools/llvm-rc/windres-preproc.test
index 52427862e760b..ad558c9a0c927 100644
--- a/llvm/test/tools/llvm-rc/windres-preproc.test
+++ b/llvm/test/tools/llvm-rc/windres-preproc.test
@@ -20,7 +20,7 @@
 ;; Test error messages when unable to execute the preprocessor.
 
 ; RUN: not llvm-windres --preprocessor intentionally-missing-executable %p/Inputs/empty.rc %t.res 2>&1 | FileCheck %s --check-prefix=CHECK4
-; CHECK4: llvm-rc: Preprocessing failed: Executable "intentionally-missing-executable" doesn't exist!
+; CHECK4: llvm-rc: Preprocessing failed: posix_spawn failed: No such file or directory
 
 ;; Test --preprocessor with an argument with spaces.
 

[mark-sed]

@arsenm The message check should probably be more general as our machine generates a different one. I have created an issue for this: #129208

[daltenty]

This seems to be encountering problems on AIX as well:
https://lab.llvm.org/buildbot/#/builders/64/builds/2371

[arsenm]

This seems to be encountering problems on AIX as well: https://lab.llvm.org/buildbot/#/builders/64/builds/2371

Should also be fixed by #129252