Assignee: unassigned at gcc dot gnu.org
Reporter: shiyan2016 at 126 dot com
Hi,
I have found a weird bug of GCC. I am trying to overwrite the C 'strncmp'
function, but I get different results when N=1 and N>1, see below test case:
/*
bug of strncmp when N=1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58240
--- Comment #2 from shiyan ---
(In reply to Paolo Carlini from comment #1)
> I can't reproduce this.
Hi,
What is your GCC version? I am using gcc4.7.2. My OS information are as below:
$lsb_release -a
No LSB modules are available.
Distributor ID:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58240
--- Comment #7 from shiyan ---
(In reply to Marc Glisse from comment #4)
> -fno-builtin (or some better such option)?
> strncmp is a standard function, your code redefining it has undefined
> behavior. gcc optimizes based on the standard behavior
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58240
--- Comment #8 from shiyan ---
(In reply to Jakub Jelinek from comment #6)
> The testcase is clearly bogus. You are not using the result of either of
> the strncmp calls, strncmp is a pure function, so it is fine not to call it
> at all.
Hi Jeli
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58240
--- Comment #9 from shiyan ---
(In reply to Paolo Carlini from comment #5)
> Closing then.
Hi Carlini,
I still think it is a bug. I know the test case is not practical. In fact, I
will not use such code in real case. But from compiler's side, th
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58240
--- Comment #13 from shiyan ---
Hi all,
Thank you for all your explanation. This seems more like a philosophical
discussion :)
I do can understand what GCC is doing (as I mentioned, it may be optimized to
*s1-*s2). And I know that this is som
