autogen.sh: CFLAGS: Add some -Werror=... flags that will be default soon

Clang 16 and GCC 14 have upgraded several warnings to errors by default.
Also, there are new warnings that will be requirements of ISO C23.  Add
all of those to our build.

Use Clang's -Wno-unknown-attribute-option, to ignore warnings that are
exclusive of GCC.  Sadly, GCC doesn't have such an option.

Link: <https://wiki.gentoo.org/wiki/Modern_C_porting#What_changed.3F>
Link: <https://github.com/shadow-maint/shadow/issues/922>
Suggested-by: Sam James <sam@gentoo.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

diff --git a/autogen.sh b/autogen.sh
index 07236426b2de464eed42d6ebfc8c7168b71ae567..a31f611cd1a83c03a4615b4cfd2a2759e0e0eaba 100755 (executable)
--- a/autogen.sh
+++ b/autogen.sh
@@ -6,7 +6,11 @@ CFLAGS="-O2"
 CFLAGS="$CFLAGS -Wall"
 CFLAGS="$CFLAGS -Wextra"
 CFLAGS="$CFLAGS -Werror=implicit-function-declaration"
+CFLAGS="$CFLAGS -Werror=implicit-int"
+CFLAGS="$CFLAGS -Werror=incompatible-pointer-types"
+CFLAGS="$CFLAGS -Werror=int-conversion"
 CFLAGS="$CFLAGS -Wno-expansion-to-defined"
+CFLAGS="$CFLAGS -Wno-unknown-warning-option"
 
 "$(dirname "$0")"/configure \
        CFLAGS="$CFLAGS" \