On 27/08/2024 22:34, Paul Eggert wrote:
I'm not seeing that false alarm when building coreutils v9.5 on Ubuntu
24.04 LTS with "./configure --enable-gcc-warnings CC=gcc-14".
What GCC version are you using? If it's not GCC 14, try upgrading. I'm
using gcc-14 (Ubuntu 14-20240412-0ubuntu1) 14.0.1 20240412
(experimental) [master r14-9935-g67e1433a94f].
I think LTO is key here, as GCC has more context then to produce warnings.
With `-march=native -O3 -flto` on GCC 14.2.1 I see,
2 false warnings in gnulib (patch attached).
1 correct warning in coreutils (patch attached).
Marking this as done.
I'll apply the patches later today.
cheers,
Pádraig.
From 264edcf263bff02aebfe67f1d7343fbf0e96b5de Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <p...@draigbrady.com>
Date: Wed, 28 Aug 2024 12:10:43 +0100
Subject: [PATCH] avoid GCC -Wmaybe-uninitialized false positives with LTO
Avoids false warnings with GCC 14.2.1 with -flto
* lib/canonicalize.c: Initialize END_IDX.
* lib/getndelim2.c: Initicalise C.
---
ChangeLog | 8 ++++++++
lib/canonicalize.c | 9 ++++++++-
lib/getndelim2.c | 8 +++++---
3 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 8a7f812b67..fdcc79134e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2024-08-28 Pádraig Brady <p...@draigbrady.com>
+
+ avoid GCC -Wmaybe-uninitialized false positives with LTO
+ Avoids false warnings with GCC 14.2.1 with -flto
+
+ * lib/canonicalize.c: Initialize END_IDX.
+ * lib/getndelim2.c: Initicalise C.
+
2024-08-28 Bruno Haible <br...@clisp.org>
doc: Add more details about O_EXEC and O_SEARCH.
diff --git a/lib/canonicalize.c b/lib/canonicalize.c
index 7d2a629024..2572b40558 100644
--- a/lib/canonicalize.c
+++ b/lib/canonicalize.c
@@ -34,6 +34,13 @@
#include "hash-triple.h"
#include "xalloc.h"
+/* Suppress bogus GCC -Wmaybe-uninitialized warnings. */
+#if defined GCC_LINT || defined lint
+# define IF_LINT(Code) Code
+#else
+# define IF_LINT(Code) /* empty */
+#endif
+
#ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
# define DOUBLE_SLASH_IS_DISTINCT_ROOT false
#endif
@@ -367,7 +374,7 @@ canonicalize_filename_mode_stk (const char *name, canonicalize_mode_t can_mode,
buf[n] = '\0';
char *extra_buf = bufs->extra.data;
- idx_t end_idx;
+ idx_t end_idx IF_LINT (= 0);
if (end_in_extra_buffer)
end_idx = end - extra_buf;
size_t len = strlen (end);
diff --git a/lib/getndelim2.c b/lib/getndelim2.c
index 89989aefdd..db61e2a5e6 100644
--- a/lib/getndelim2.c
+++ b/lib/getndelim2.c
@@ -47,8 +47,10 @@
#include "memchr2.h"
/* Avoid false GCC warning "'c' may be used uninitialized". */
-#if _GL_GNUC_PREREQ (4, 7)
-# pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#if defined GCC_LINT || defined lint
+# define IF_LINT(Code) Code
+#else
+# define IF_LINT(Code) /* empty */
#endif
/* The maximum value that getndelim2 can return without suffering from
@@ -102,7 +104,7 @@ getndelim2 (char **lineptr, size_t *linesize, size_t offset, size_t nmax,
/* Here always ptr + size == read_pos + nbytes_avail.
Also nbytes_avail > 0 || size < nmax. */
- int c;
+ int c IF_LINT (= EOF);
const char *buffer;
size_t buffer_len;
--
2.46.0
From 9b9763e6a7499d78373fb42bac3dc2ee68a14b69 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <p...@draigbrady.com>
Date: Wed, 28 Aug 2024 12:33:17 +0100
Subject: [PATCH] all: fix error checking in gl/lib/xdectoint.c
This issue was noticed with -flto on GCC 14.2.1
* gl/lib/xdectoint.c (__xnumtoint): Only inspect the
returned value if LONGINT_INVALID is not set,
as the returned value is uninitialized in that case.
Fixes https://bugs.gnu.org/72842
---
gl/lib/xdectoint.c | 37 ++++++++++++++++++++-----------------
1 file changed, 20 insertions(+), 17 deletions(-)
diff --git a/gl/lib/xdectoint.c b/gl/lib/xdectoint.c
index bb38431f3..05534701c 100644
--- a/gl/lib/xdectoint.c
+++ b/gl/lib/xdectoint.c
@@ -49,24 +49,27 @@ __xnumtoint (char const *n_str, int base, __xdectoint_t min, __xdectoint_t max,
/* Errno value to report if there is an overflow. */
int overflow_errno;
- if (tnum < min)
+ if (s_err != LONGINT_INVALID)
{
- r = min;
- overflow_errno = flags & XTOINT_MIN_RANGE ? ERANGE : EOVERFLOW;
- if (s_err == LONGINT_OK)
- s_err = LONGINT_OVERFLOW;
- }
- else if (max < tnum)
- {
- r = max;
- overflow_errno = flags & XTOINT_MAX_RANGE ? ERANGE : EOVERFLOW;
- if (s_err == LONGINT_OK)
- s_err = LONGINT_OVERFLOW;
- }
- else
- {
- r = tnum;
- overflow_errno = EOVERFLOW;
+ if (tnum < min)
+ {
+ r = min;
+ overflow_errno = flags & XTOINT_MIN_RANGE ? ERANGE : EOVERFLOW;
+ if (s_err == LONGINT_OK)
+ s_err = LONGINT_OVERFLOW;
+ }
+ else if (max < tnum)
+ {
+ r = max;
+ overflow_errno = flags & XTOINT_MAX_RANGE ? ERANGE : EOVERFLOW;
+ if (s_err == LONGINT_OK)
+ s_err = LONGINT_OVERFLOW;
+ }
+ else
+ {
+ r = tnum;
+ overflow_errno = EOVERFLOW;
+ }
}
int e = s_err == LONGINT_OVERFLOW ? overflow_errno : 0;
--
2.46.0
