[Valgrind-developers] [valgrind] configure and make: add configure checks for C++ exception warnings

[Paul F. <pa...@so...>]

https://sourceware.org/cgit/valgrind/commit/?id=5b6a8d27e717dc71818e0b8b28b6d41e377f4b84

commit 5b6a8d27e717dc71818e0b8b28b6d41e377f4b84
Author: Paul Floyd <pj...@wa...>
Date:   Mon Oct 13 08:38:09 2025 +0200

    configure and make: add configure checks for C++ exception warnings
    
    Add checks for -Wno-implicit-exception-spec-mismatch
       (FLAG_W_NO_IMPLICIT_EXCEPTION_SPEC_MISMATCH)
    and -Wno-missing-exception-spec
       (FLAG_W_NO_MISSING_EXCEPTION_SPEC)
    
    Also we should clean up C++ flag checking a bit. If all checks get
    grouped together than just one AC_LANG(C++)/AC_LANG(C) would be
    needed.

Diff:
---
 configure.ac             | 18 ++++++++++++++++++
 massif/tests/Makefile.am |  2 +-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 1a7ea34d1b..9217aa0ac8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2638,6 +2638,24 @@ AC_GCC_WARNING_SUBST([logical-op], [FLAG_W_LOGICAL_OP])
 AC_GCC_WARNING_SUBST([enum-conversion], [FLAG_W_ENUM_CONVERSION])
 AC_GCC_WARNING_SUBST([implicit-fallthrough=2], [FLAG_W_IMPLICIT_FALLTHROUGH])
 
+# as above, C++ flags
+AC_DEFUN([AC_GXX_WARNING_SUBST_NO],[
+  AC_MSG_CHECKING([if g++ accepts -W$1])
+  safe_CXXFLAGS=$CXXFLAGS
+  CXXFLAGS="-W$1 -Werror"
+  AC_LANG_PUSH(C++)
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[;]])], [
+                    AC_SUBST([$2], [-Wno-$1])
+  AC_LANG_POP()
+  AC_MSG_RESULT([yes])], [
+                AC_SUBST([$2], [])
+                AC_MSG_RESULT([no])])
+  CXXFLAGS=$safe_CXXFLAGS
+])
+
+AC_GXX_WARNING_SUBST_NO([missing-exception-spec], [FLAG_W_NO_MISSING_EXCEPTION_SPEC])
+AC_GXX_WARNING_SUBST_NO([implicit-exception-spec-mismatch], [FLAG_W_NO_IMPLICIT_EXCEPTION_SPEC_MISMATCH])
+
 # Does this compiler support -Wformat-security ?
 # Special handling is needed, because certain GCC versions require -Wformat
 # being present if -Wformat-security is given. Otherwise a warning is issued.
diff --git a/massif/tests/Makefile.am b/massif/tests/Makefile.am
index d4d798f69c..b596592727 100644
--- a/massif/tests/Makefile.am
+++ b/massif/tests/Makefile.am
@@ -98,7 +98,7 @@ bug469146_CXXFLAGS	= $(AM_CXXFLAGS) -O2 -fno-optimize-sibling-calls @FLAG_W_NO_U
 new_cpp_SOURCES		= new-cpp.cpp
 overloaded_new_SOURCES	= overloaded-new.cpp
 # aligned new needs C++17
-overloaded_new_CXXFLAGS	= $(AM_CXXFLAGS) -Wno-implicit-exception-spec-mismatch -Wno-missing-exception-spec -std=c++17
+overloaded_new_CXXFLAGS	= $(AM_CXXFLAGS) @FLAG_W_NO_IMPLICIT_EXCEPTION_SPEC_MISMATCH@ @FLAG_W_NO_MISSING_EXCEPTION_SPEC@ -std=c++17
 
 # Suppress warnings for issues we are testing for
 alloc_fns_CFLAGS	= $(AM_CFLAGS) -Wno-unused-result