manywarnings: update C warnings for GCC 13

Adjust for C programs compiled by GCC 13.
(A C++ expert still needs to look at manywarnings-c++.m4.)
* build-aux/gcc-warning.spec: Add warnings introduced in GCC 13.
* doc/manywarnings.texi (manywarnings): Document flex arrays.
* m4/manywarnings.m4 (gl_MANYWARN_ALL_GCC): Add
-fstrict-flex-arrays and -Wstrict-flex-arrays as these should be
suitable for Gnulib-using code.

4 files changed, 48 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 5246e88037..ff1f6abca3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,14 @@
 2023-04-23  Paul Eggert  <eggert@cs.ucla.edu>
 
+	manywarnings: update C warnings for GCC 13
+	Adjust for C programs compiled by GCC 13.
+	(A C++ expert still needs to look at manywarnings-c++.m4.)
+	* build-aux/gcc-warning.spec: Add warnings introduced in GCC 13.
+	* doc/manywarnings.texi (manywarnings): Document flex arrays.
+	* m4/manywarnings.m4 (gl_MANYWARN_ALL_GCC): Add
+	-fstrict-flex-arrays and -Wstrict-flex-arrays as these should be
+	suitable for Gnulib-using code.
+
 	manywarnings: bring doc up to date
 	* doc/manywarnings.texi: Bring doc up to date for GCC 12.
 
diff --git a/build-aux/gcc-warning.spec b/build-aux/gcc-warning.spec
index cbcbc87f9a..09350012ba 100644
--- a/build-aux/gcc-warning.spec
+++ b/build-aux/gcc-warning.spec
@@ -18,25 +18,45 @@
 -Walloca				we like alloca in small doses
 -Walloca-larger-than=<number>		FIXME: choose something sane?
 -Wampersand				fortran
+-Wanalyzer-allocation-size		enabled by -fanalyzer
+-Wanalyzer-deref-before-check		enabled by -fanalyzer
 -Wanalyzer-double-fclose		enabled by -fanalyzer
 -Wanalyzer-double-free			enabled by -fanalyzer
 -Wanalyzer-exposure-through-output-file	enabled by -fanalyzer
+-Wanalyzer-exposure-through-uninit-copy	enabled by -fanalyzer
+-Wanalyzer-fd-access-mode-mismatch	enabled by -fanalyzer
+-Wanalyzer-fd-double-close		enabled by -fanalyzer
+-Wanalyzer-fd-leak			enabled by -fanalyzer
+-Wanalyzer-fd-phase-mismatch		enabled by -fanalyzer
+-Wanalyzer-fd-type-mismatch		enabled by -fanalyzer
+-Wanalyzer-fd-use-after-close		enabled by -fanalyzer
+-Wanalyzer-fd-use-without-check		enabled by -fanalyzer
 -Wanalyzer-file-leak			enabled by -fanalyzer
 -Wanalyzer-free-of-non-heap		enabled by -fanalyzer
+-Wanalyzer-imprecise-fp-arithmetic	enabled by -fanalyzer
+-Wanalyzer-infinite-recursion		enabled by -fanalyzer
+-Wanalyzer-jump-through-null		enabled by -fanalyzer
 -Wanalyzer-malloc-leak			enabled by -fanalyzer
 -Wanalyzer-mismatching-deallocation	enabled by -fanalyzer
 -Wanalyzer-null-argument		enabled by -fanalyzer
 -Wanalyzer-null-dereference		enabled by -fanalyzer
+-Wanalyzer-out-of-bounds		enabled by -fanalyzer
 -Wanalyzer-possible-null-argument	enabled by -fanalyzer
 -Wanalyzer-possible-null-dereference	enabled by -fanalyzer
+-Wanalyzer-putenv-of-auto-var		enabled by -fanalyzer
 -Wanalyzer-shift-count-negative		enabled by -fanalyzer
 -Wanalyzer-shift-count-overflow		enabled by -fanalyzer
 -Wanalyzer-stale-setjmp-buffer		implied by -fanalyzer
 -Wanalyzer-tainted-allocation-size	FIXME requires -fanalyzer-checker=taint
 -Wanalyzer-tainted-array-index		FIXME requires -fanalyzer-checker=taint
+-Wanalyzer-tainted-assertion		FIXME requires -fanalyzer-checker=taint
 -Wanalyzer-tainted-divisor		FIXME requires -fanalyzer-checker=taint
 -Wanalyzer-tainted-offset		FIXME requires -fanalyzer-checker=taint
 -Wanalyzer-tainted-size			FIXME requires -fanalyzer-checker=taint
+-Wanalyzer-va-arg-type-mismatch		enabled by -fanalyzer
+-Wanalyzer-va-list-exhausted		enabled by -fanalyzer
+-Wanalyzer-va-list-leak			enabled by -fanalyzer
+-Wanalyzer-va-list-use-after-va-end	enabled by -fanalyzer
 -Wanalyzer-too-complex			enabled by -fanalyzer
 -Wanalyzer-unsafe-call-within-signal-handler	enabled by -fanalyzer
 -Wanalyzer-use-after-free		enabled by -fanalyzer
@@ -85,6 +105,7 @@
 -Wcast-result				D
 -Wcatch-value				c++
 -Wcatch-value=<0,3>			c++
+-Wchanges-meaning			c++
 -Wchar-subscripts			enabled by -Wall
 -Wcharacter-truncation			fortran
 -Wchkp					deprecated
@@ -95,6 +116,7 @@
 -Wcomment				enabled by -Wall
 -Wcomments				alias for -Wcomment
 -Wcompare-reals				fortran
+-Wcomplain-wrong-lang			default
 -Wconditionally-supported		c++ and objc++
 -Wconversion				FIXME maybe? too much noise; encourages bad changes
 -Wconversion-extra			fortran
@@ -107,6 +129,7 @@
 -Wdangling-else				enabled by -Wparentheses
 -Wdangling-pointer			enabled by -Wall
 -Wdangling-pointer=<0,2>		enabled by -Wall
+-Wdangling-reference			c++ and objc++
 -Wdeclaration-after-statement		needed only for pre-C99, so obsolete
 -Wdelete-incomplete			c++ and objc++
 -Wdelete-non-virtual-dtor		c++
@@ -126,6 +149,7 @@
 -Wempty-body				enabled by -Wextra
 -Wenum-compare				enabled by -Wall
 -Wenum-conversion			enabled by -Wextra
+-Wenum-int-mismatch			enabled by -Wall
 -Wendif-labels				default
 -Werror-implicit-function-declaration	deprecated
 -Wexceptions				c++ and objc++
@@ -173,9 +197,11 @@
 -Winterference-size			c++
 -Wintrinsic-shadow			fortran
 -Wintrinsics-std			fortran
+-Winvalid-constexpr			c++
 -Winvalid-imported-macros		c++ and objc++
 -Winvalid-memory-model			default
 -Winvalid-offsetof			c++ and objc++
+-Winvalid-utf8				enabled by -finput-charset=UTF-8
 -Wjump-misses-init			only useful for code meant to be compiled by a C++ compiler
 -Wlarger-than-				gcc --help=warnings artifact
 -Wlarger-than=<byte-size>		FIXME: choose something sane?
@@ -228,6 +254,7 @@
 -Wopenacc-parallelism			OpenACC
 -Woverflow				default
 -Woverloaded-virtual			c++
+-Woverloaded-virtual=<0,2>		c++
 -Woverride-init				enabled by -Wextra
 -Woverride-init-side-effects		c++ and objc++
 -Woverwrite-recursive			fortran
@@ -263,6 +290,7 @@
 -Wscalar-storage-order			default
 -Wselector				objc and objc++
 -Wsequence-point			enabled by -Wall
+-Wself-move				c++ and objc++
 -Wshadow-compatible-local		covered by -Wshadow
 -Wshadow-ivar				objc
 -Wshadow-local				covered by -Wshadow
@@ -318,6 +346,7 @@
 -Wundef					FIXME maybe? too many false positives
 -Wundefined-do-loop			fortran
 -Wunderflow				fortran
+-Wunicode				default
 -Wunreachable-code			obsolescent no-op
 -Wunsuffixed-float-constants		triggers warning in gnulib's timespec.h
 -Wunused				enabled by -Wall
@@ -345,6 +374,7 @@
 -Wvla-parameter				enabled by -Wall
 -Wvolatile				c++ and objc++
 -Wvolatile-register-var			enabled by -Wall
+-Wxor-used-as-pow			default
 -Wzero-as-null-pointer-constant		c++ and objc++
 -Wzero-length-bounds			enabled by -Wall
 -Wzerotrip				fortran
diff --git a/doc/manywarnings.texi b/doc/manywarnings.texi
index 32237dc67f..ea1b758cc0 100644
--- a/doc/manywarnings.texi
+++ b/doc/manywarnings.texi
@@ -80,6 +80,13 @@ The @code{-fanalyzer} option generates many false alarms about
 @code{malloc} leaks, which @code{manywarnings} suppresses by also
 using @option{-Wno-analyzer-malloc-leak}.
 
+@item -fstrict-flex-arrays
+The @code{manywarnings} module by default uses GCC's
+@option{-fstrict-flex-arrays} option if available, so that GCC can
+warn about nonportable usage of flexible array members.
+In a few cases this can help GCC generate better code,
+so it is not strictly a warning option.
+
 @item -Wsign-compare
 GCC and Clang generate too many false alarms with @option{-Wsign-compare},
 and we don't recommend that warning.  You can disable it by using
diff --git a/m4/manywarnings.m4 b/m4/manywarnings.m4
index f88dcc5f12..1d69116ddb 100644
--- a/m4/manywarnings.m4
+++ b/m4/manywarnings.m4
@@ -109,7 +109,7 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC(C)],
   #  <(LC_ALL=C gcc --help=warnings | sed -n 's/^  \(-[^ ]*\) .*/\1/p' | sort)
 
   $1=
-  for gl_manywarn_item in -fanalyzer \
+  for gl_manywarn_item in -fanalyzer -fstrict-flex-arrays \
     -Wall \
     -Warith-conversion \
     -Wbad-function-cast \
@@ -137,6 +137,7 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC(C)],
     -Wpointer-arith \
     -Wshadow \
     -Wstack-protector \
+    -Wstrict-flex-arrays \
     -Wstrict-overflow \
     -Wstrict-prototypes \
     -Wsuggest-attribute=cold \