Revert "Reapply: Add an error message to the default SIGPIPE handler"

This patch is spamming compiles with unhelpful and confusing messages.
E.g. the Linux kernel uses "grep -q" in several places. It's meant to
quit with a return code of zero when the first match is found. This can
cause a SIGPIPE signal, but that's expected, and there's no way to turn
this error message off to avoid spurious error messages.

UNIX03 apparently doesn't require printing an error message on SIGPIPE,
but specifically when there's an error on the stdout stream in a normal
program flow, e.g. when SIGPIPE trap is disabled.

A separate patch is planned to address the specific case we care most
about (involving llvm-nm).

This reverts commit b89bcefa6202e310eb3167dd1c37f1807377ec8d.

Link: https://github.com/llvm/llvm-project/issues/59037
Link: https://github.com/ClangBuiltLinux/linux/issues/1651
Differential Revision: https://reviews.llvm.org/D138244

diff --git a/llvm/lib/Support/Unix/Signals.inc b/llvm/lib/Support/Unix/Signals.inc
index 3c34da8..b07d319 100644 (file)
--- a/llvm/lib/Support/Unix/Signals.inc
+++ b/llvm/lib/Support/Unix/Signals.inc
@@ -432,10 +432,6 @@ void llvm::sys::SetOneShotPipeSignalFunction(void (*Handler)()) {
 }
 
 void llvm::sys::DefaultOneShotPipeSignalHandler() {
-  // UNIX03 conformance requires a non-zero exit code and an error message
-  // to stderr when writing to a closed stdout fails.
-  errs() << "error: write on a pipe with no reader\n";
-
   // Send a special return code that drivers can check for, from sysexits.h.
   exit(EX_IOERR);
 }

diff --git a/llvm/test/Support/unix03-sigpipe-exit.test b/llvm/test/Support/unix03-sigpipe-exit.test
deleted file mode 100644 (file)
index 0168084..0000000
--- a/llvm/test/Support/unix03-sigpipe-exit.test
+++ /dev/null
@@ -1,26 +0,0 @@
-## Test that when writing to a closed stdout, LLVM tools finish with a non-zero
-## exit code and an error message on stderr. The test uses llvm-cxxfilt, but
-## it's a logic from the default SIGPIPE handler, so it applies to all the tools.
-## This is required for UNIX03 conformance.
-
-# UNSUPPORTED: system-windows
-
-# RUN: not %python %s llvm-cxxfilt 2>&1 | FileCheck %s
-# CHECK: error: write on a pipe with no reader
-
-import subprocess
-import sys
-
-with subprocess.Popen([sys.argv[1]], stdout=subprocess.PIPE, stdin=subprocess.PIPE) as process:
-  process.stdout.close()
-
-  # llvm-cxxfilt with no extra arguments runs interactively and writes input
-  # to output. Writing continuously to stdin should trigger SIGPIPE when the
-  # subprocess attempts to write out bytes to a closed stdout.
-  try:
-    while True:
-      process.stdin.write("foo\n".encode("utf-8"))
-  except BrokenPipeError:
-    # Clear stdin, pipe is broken and closing it on cleanup will raise an exception.
-    process.stdin = None
-sys.exit(process.returncode)