From 245c132218f792a1e8a1bdd80ea08b73bf87e356 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 30 Apr 2026 11:48:47 +0930
Subject: [PATCH] Build: Only use -Werror on debug builds.

Otherwise, we can break people's builds if they upgrade compiler, for example.

Yet we still want -Werror for developers, and CI.

Changelog-Changed: Build: We no longer use `-Werror` by default, unless --enable-debugbuild is set.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 configure | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/configure b/configure
index bee8ab193574ead6251cece2a5962594a2c89816..0aa1669ab9bc25999071d4551724924bc572e136 100755
--- a/configure
+++ b/configure
@@ -6,7 +6,7 @@ set -e
 CONFIGURATOR=ccan/tools/configurator/configurator
 CONFIG_VAR_FILE=config.vars
 CONFIG_HEADER=ccan/config.h
-BASE_WARNFLAGS="-Wall -Wundef -Wmissing-prototypes -Wmissing-declarations -Wstrict-prototypes -Wold-style-definition -Werror"
+BASE_WARNFLAGS="-Wall -Wundef -Wmissing-prototypes -Wmissing-declarations -Wstrict-prototypes -Wold-style-definition"
 
 OS=$(uname -s)
 ARCH=$(uname -m)
@@ -51,7 +51,7 @@ default_coptflags()
     fi
 }
 
-# Given COPTFLAGS, HAVE_GCC and HAVE_MODERN_GCC, what CWARNFLAGS to default to?
+# Given COPTFLAGS, HAVE_GCC, HAVE_MODERN_GCC and DEBUGBUILD, what CWARNFLAGS to default to?
 default_cwarnflags()
 {
     F=$BASE_WARNFLAGS
@@ -66,6 +66,10 @@ default_cwarnflags()
 	# this gcc-only.
 	F="$F -Wshadow=local"
     fi
+    # Debug builds get -Werror (great for CI!)
+    if [ "$4" = 1 ]; then
+	F="$F -Werror"
+    fi
     echo "$F"
 }
 
@@ -220,7 +224,8 @@ have_function_sections()
     TMPOBJFILE=$CONFIG_VAR_FILE.$$.o
     
     echo "int foo(void); int foo(void) { return 0; }" > $TMPCFILE
-    $1 $2 -ffunction-sections -Wl,--gc-sections -c $TMPCFILE -o $TMPOBJFILE
+    # We *want* this to fail if we get a warning, hence use -Werror.
+    $1 $2 -Werror -ffunction-sections -Wl,--gc-sections -c $TMPCFILE -o $TMPOBJFILE
 }
 
 usage()
@@ -231,7 +236,7 @@ usage()
     set_defaults
     DEFAULT_COPTFLAGS="$(default_coptflags $DEBUGBUILD)"
     # We assume we have a modern gcc.
-    DEFAULT_CWARNFLAGS="$(default_cwarnflags ""$DEFAULT_COPTFLAGS"" 1 1)"
+    DEFAULT_CWARNFLAGS="$(default_cwarnflags ""$DEFAULT_COPTFLAGS"" 1 1 ""$DEBUGBUILD"")"
     usage_with_default "CC" "$CC"
     usage_with_default "CWARNFLAGS" "$DEFAULT_CWARNFLAGS"
     usage_with_default "COPTFLAGS" "$DEFAULT_COPTFLAGS"
@@ -601,7 +606,8 @@ fi
 if [ -z ${CWARNFLAGS+x} ]; then
     CWARNFLAGS=$(default_cwarnflags "$COPTFLAGS" \
 		    $(sed -n 's/^HAVE_GCC=//p' < $CONFIG_VAR_FILE.$$) \
-		    $(sed -n 's/^HAVE_MODERN_GCC=//p' < $CONFIG_VAR_FILE.$$) )
+		    $(sed -n 's/^HAVE_MODERN_GCC=//p' < $CONFIG_VAR_FILE.$$) \
+		    "$DEBUGBUILD")
 fi
 
 add_var PREFIX "$PREFIX"