scripts/Makefile.extrawarn: Respect CONFIG_WERROR / W=e for hostprogs

Commit 27758d8c2583 ("kbuild: enable -Werror for hostprogs")
unconditionally enabled -Werror for the compiler, assembler, and linker
when building the host programs, as the build footprint of the host
programs is small (thus risk of build failures from warnings are low)
and that stage of the build may not have Kconfig values (thus
CONFIG_WERROR could not be used as a precondition).

While turning warnings into errors unconditionally happens in a few
places within the kernel, it can be disruptive to people who may be
building with newer compilers, such as while doing a bisect. While it is
possible to avoid this behavior by passing HOSTCFLAGS=-w or
HOSTCFLAGS=-Wno-error, it may not be the most intuitive for regular
users not intimately familiar with Kbuild.

Avoid being disruptive to the entire build by depending on the explicit
opt-in of CONFIG_WERROR or W=e to enable -Werror and the like while
building the host programs. While this means there is a small portion of
the build that does not have -Werror enabled (namely scripts/kconfig/*
and scripts/basic/fixdep), it is better than not having it altogether.

Fixes: 27758d8c2583 ("kbuild: enable -Werror for hostprogs")
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reported-by: Askar Safin <safinaskar@gmail.com>
Closes: https://lore.kernel.org/20251005011100.1035272-1-safinaskar@gmail.com/
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Tested-by: Miguel Ojeda <ojeda@kernel.org> # Rust
Link: https://patch.msgid.link/20251006-kbuild-hostprogs-werror-fix-v1-1-23cf1ffced5c@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 1434cb6208cb82f20aeb29cc8c059220d1a1f6d2..6af392f9cd0227449db8bcfb97d8bad4dfbe3a8e 100644 (file)
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -223,9 +223,11 @@ KBUILD_USERCFLAGS  += -Werror
 KBUILD_USERLDFLAGS     += -Wl,--fatal-warnings
 KBUILD_RUSTFLAGS       += -Dwarnings
 
-endif
-
-# Hostprog flags are used during build bootstrapping and can not rely on CONFIG_ symbols.
+# While hostprog flags are used during build bootstrapping (thus should not
+# depend on CONFIG_ symbols), -Werror is disruptive and should be opted into.
+# Only apply -Werror to hostprogs built after the initial Kconfig stage.
 KBUILD_HOSTCFLAGS      += -Werror
 KBUILD_HOSTLDFLAGS     += -Wl,--fatal-warnings
 KBUILD_HOSTRUSTFLAGS   += -Dwarnings
+
+endif