From 31d16f02761c05f3159813be269e50c0c42000d4 Mon Sep 17 00:00:00 2001
From: Duane Griffin <duaneg@dghda.com>
Date: Fri, 30 May 2025 11:15:45 +1200
Subject: [PATCH] gh-117888: print failing command when platform triplet
 detection errors

The build system determines the platform triplet using the C preprocessor. If
that fails for whatever reason we presently just report "none" for the triplet
and continue until the invalid triplet causes a messy failure down the line.

Instead, store any error output, and in the event of a failure send it to
stderr and fail immediately with a clear error message.
---
 .../Build/2025-05-30-11-19-19.gh-issue-117888.-4okIx.rst    | 1 +
 configure                                                   | 6 +++---
 configure.ac                                                | 5 +++--
 3 files changed, 7 insertions(+), 5 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Build/2025-05-30-11-19-19.gh-issue-117888.-4okIx.rst

diff --git a/Misc/NEWS.d/next/Build/2025-05-30-11-19-19.gh-issue-117888.-4okIx.rst b/Misc/NEWS.d/next/Build/2025-05-30-11-19-19.gh-issue-117888.-4okIx.rst
new file mode 100644
index 00000000000000..1fd1af6b654ea1
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2025-05-30-11-19-19.gh-issue-117888.-4okIx.rst
@@ -0,0 +1 @@
+Report error if platform triplet detection fails.
diff --git a/configure b/configure
index c9ce9b4a73527d..b4e36d1b1af040 100755
--- a/configure
+++ b/configure
@@ -7161,14 +7161,14 @@ fi
 
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for the platform triplet based on compiler characteristics" >&5
 printf %s "checking for the platform triplet based on compiler characteristics... " >&6; }
-if $CPP $CPPFLAGS $srcdir/Misc/platform_triplet.c >conftest.out 2>/dev/null; then
+if $CPP $CPPFLAGS $srcdir/Misc/platform_triplet.c >conftest.out 2>conftest.err; then
   PLATFORM_TRIPLET=`grep '^PLATFORM_TRIPLET=' conftest.out | tr -d ' 	'`
   PLATFORM_TRIPLET="${PLATFORM_TRIPLET#PLATFORM_TRIPLET=}"
   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $PLATFORM_TRIPLET" >&5
 printf "%s\n" "$PLATFORM_TRIPLET" >&6; }
 else
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: none" >&5
-printf "%s\n" "none" >&6; }
+  cat conftest.err >&2
+  as_fn_error $? "platform triplet detection failed, see error output above" "$LINENO" 5
 fi
 rm -f conftest.out
 
diff --git a/configure.ac b/configure.ac
index eb52365d95be21..22e10b5e8d4fd2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1151,12 +1151,13 @@ fi
 
 
 AC_MSG_CHECKING([for the platform triplet based on compiler characteristics])
-if $CPP $CPPFLAGS $srcdir/Misc/platform_triplet.c >conftest.out 2>/dev/null; then
+if $CPP $CPPFLAGS $srcdir/Misc/platform_triplet.c >conftest.out 2>conftest.err; then
   PLATFORM_TRIPLET=`grep '^PLATFORM_TRIPLET=' conftest.out | tr -d ' 	'`
   PLATFORM_TRIPLET="${PLATFORM_TRIPLET@%:@PLATFORM_TRIPLET=}"
   AC_MSG_RESULT([$PLATFORM_TRIPLET])
 else
-  AC_MSG_RESULT([none])
+  cat conftest.err >&2
+  AC_MSG_ERROR([platform triplet detection failed, see error output above])
 fi
 rm -f conftest.out