From 6163c922a2064131c51ea664c0ed684b427d9e88 Mon Sep 17 00:00:00 2001
From: Pratyush Sharma <56130065+pratyush618@users.noreply.github.com>
Date: Sun, 26 Apr 2026 23:31:34 +0530
Subject: [PATCH] gh-149021: Fix AIX build by dropping `-e` from `SHELL`

AIX make treats `SHELL` as a literal executable path, so
`SHELL = /bin/sh -e` (added in gh-100220) failed with
`/bin/sh -e: not found`. Use `.POSIX:` instead, which makes both
POSIX make and GNU make invoke the shell with `-e`.
---
 Makefile.pre.in                                      | 12 ++++++++++--
 .../2026-04-26-12-00-00.gh-issue-149021.vo85dd.rst   |  6 ++++++
 2 files changed, 16 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Build/2026-04-26-12-00-00.gh-issue-149021.vo85dd.rst

diff --git a/Makefile.pre.in b/Makefile.pre.in
index 8b46db33a2ac18..61a770dba0106c 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -18,6 +18,12 @@
 #
 # See also the section "Build instructions" in the README file.
 
+# Run in POSIX-conforming mode. Among other things this guarantees that the
+# shell is invoked with -e (so complex recipes fail on the first error),
+# which avoids relying on SHELL = /bin/sh -e -- AIX make interprets that as
+# a literal path and fails to find an executable named "/bin/sh -e".
+.POSIX:
+
 # === Variables set by makesetup ===
 
 MODBUILT_NAMES=    _MODBUILT_NAMES_
@@ -61,8 +67,10 @@ DSYMUTIL_PATH=  @DSYMUTIL_PATH@
 
 GNULD=		@GNULD@
 
-# Shell used by make (some versions default to the login shell, which is bad)
-SHELL=		/bin/sh -e
+# Shell used by make (some versions default to the login shell, which is bad).
+# The shell is invoked with -e via the .POSIX: special target above, which
+# applies under POSIX make implementations and to GNU make in POSIX mode.
+SHELL=		/bin/sh
 
 # Use this to make a link between python$(VERSION) and python in $(BINDIR)
 LN=		@LN@
diff --git a/Misc/NEWS.d/next/Build/2026-04-26-12-00-00.gh-issue-149021.vo85dd.rst b/Misc/NEWS.d/next/Build/2026-04-26-12-00-00.gh-issue-149021.vo85dd.rst
new file mode 100644
index 00000000000000..c6cc9946962c72
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2026-04-26-12-00-00.gh-issue-149021.vo85dd.rst
@@ -0,0 +1,6 @@
+Fix build on AIX by no longer setting ``SHELL = /bin/sh -e`` in the
+top-level :file:`Makefile`.  AIX :program:`make` interprets ``SHELL`` as a
+literal executable path, so the embedded ``-e`` flag caused
+:samp:`/bin/sh -e: not found`.  The makefile now sets ``SHELL = /bin/sh``
+and declares the ``.POSIX:`` special target, which causes both POSIX
+:program:`make` and GNU :program:`make` to invoke the shell with ``-e``.