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Re: test-free: fails with -flto=auto
From: |
Bruno Haible |
Subject: |
Re: test-free: fails with -flto=auto |
Date: |
Sun, 03 Jan 2021 11:21:21 +0100 |
User-agent: |
KMail/5.1.3 (Linux/4.4.0-197-generic; KDE/5.18.0; x86_64; ; ) |
Hi Berny,
> hmm, I tried a couple of things like declaring the variable err as static.
> The only combination I found to work is:
>
> diff --git a/lib/free.c b/lib/free.c
> index 135c3eb..e923ee5 100644
> --- a/lib/free.c
> +++ b/lib/free.c
> @@ -27,7 +27,10 @@ void
> rpl_free (void *p)
> #undef free
> {
> - int err = errno;
> + int err[2];
> + err[0] = errno;
> + err[1] = errno;
> + errno = 0;
> free (p);
> - errno = err;
> + errno = err[errno==0];
> }
>
> It's slow and ugly. ;-(
It's not that slow. I like it :-) Installed as follows:
2021-01-03 Bruno Haible <bruno@clisp.org>
free-posix: Work around GCC mis-optimization bug.
Code by Bernhard Voelker <mail@bernhard-voelker.de>.
* lib/free.c (rpl_free): Add alternative complicated code for GCC.
diff --git a/lib/free.c b/lib/free.c
index 135c3eb..5c89787 100644
--- a/lib/free.c
+++ b/lib/free.c
@@ -27,7 +27,21 @@ void
rpl_free (void *p)
#undef free
{
+#if defined __GNUC__ && !defined __clang__
+ /* An invalid GCC optimization
+ <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98396>
+ would optimize away the assignments in the code below, when link-time
+ optimization (LTO) is enabled. Make the code more complicated, so that
+ GCC does not grok how to optimize it. */
+ int err[2];
+ err[0] = errno;
+ err[1] = errno;
+ errno = 0;
+ free (p);
+ errno = err[errno == 0];
+#else
int err = errno;
free (p);
errno = err;
+#endif
}