compile with gcc option -O0 or -O

[David Brown]

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