From: David Brown <david@westcontrol.com>
To: gcc-help@gcc.gnu.org
Subject: Re: compile with gcc option -O0 or -O
Date: Fri, 16 Sep 2011 07:10:00 -0000 [thread overview]
Message-ID: <j4usou$v7p$1@dough.gmane.org> (raw)
In-Reply-To: <mcrobyl6o4f.fsf@coign.corp.google.com>
On 16/09/2011 07:40, Ian Lance Taylor wrote:
> zou wonder<wonder.zou@gmail.com> writes:
>
>> but one weird problem is that the following codes compiled with option -O0
>
> You need to show us a small complete self-contained example.
>
> Normally a program which works at -O0 and fails at -O1 has an
> uninitialized variable somewhere.
>
> Ian
>
Another common cause is aliasing - using pointer casts to access the
same data in different ways.
And (especially if this is embedded programming), also check for missing
"volatile" qualifiers.
Compile your code with lots of warnings - that will help spot mistakes.
The flags I often use are:
-Wall
-Wextra
-Winit-self
-Wmissing-include-dirs
-Wunused
-Wstrict-overflow
-Wfloat-equal
-Wundef
-Wunsafe-loop-optimizations
-Wpointer-arith
-Wcast-qual
-Wcast-align
-Wwrite-strings
-Wlogical-op
-Wmissing-declarations
-Wmissing-noreturn
-Wmissing-format-attribute
-Winline
-Wnested-externs
-Wdisabled-optimization
-Wunsafe-loop-optimizations
-Wpadded
-Wunreachable-code
-Wmissing-prototypes
-Wredundant-decls
-Wcast-qual
-Wcast-align
-Wpointer-arith
-Wnested-externs
-Wno-multichar
next prev parent reply other threads:[~2011-09-16 7:10 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-16 5:04 zou wonder
2011-09-16 5:41 ` Ian Lance Taylor
2011-09-16 7:10 ` David Brown [this message]
2011-09-16 7:54 ` Miles Bader
2011-09-16 9:21 ` David Brown
2011-09-16 10:06 ` Miles Bader
2011-09-16 10:35 ` David Brown
2011-09-16 8:27 ` Jeffrey Walton
[not found] ` <CAOXjUBzK0snvjNcpi8D3mK5dmXwzH62XXETyjv+4f6S+LDmXyQ@mail.gmail.com>
[not found] ` <CAOXjUBwW2ghmfsF1OA5DY7hZOz-43r22biSG60VyWaviFau_-Q@mail.gmail.com>
[not found] ` <mcrfwjx6lrk.fsf@coign.corp.google.com>
2011-09-16 9:12 ` zou wonder
2011-09-16 9:32 ` David Brown
2011-09-16 9:47 ` Jonathan Wakely
2011-09-19 9:57 ` zou wonder
2011-09-19 10:32 ` David Brown
2011-09-21 2:18 ` zou wonder
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