[Solved] Same C code, different result on x86 and ARM

[Linux-SWAT]

Hi,

this is a Sobel filter.
It compiles on x86_64 and ARM 32 and 64, and must be used with a 8bit grayscale .bmp .

The problem is that the execution on ARM 32 and 64 produces a garbage image, and I have absolutely no idea why.

I tried GCC 5 and 7 on ARM64.

Any thoughts ?

 

[elvissteinjr]

I didn't test the code, but to me it looks like the unaligned memory access you do with the short pointers may be the culprit. You can get away with that on x86, but not ARM iirc.

 

[ptitSeb]

Maybe it's just the structure that need packing.
try to add

#pragma pack(push, 1)

befor the definition of the struct in the .h
and

#pragma pack(pop)

aftrer the definition

 

[Linux-SWAT]

Pragma didn't help.

 

[PokeParadox]

It could be a different signedness of the bytes between x86/ARM?

 

[ptitSeb]

Ah yes, it's important to build with "-fsigned-char" on ARM...

 

[Linux-SWAT]

Ah yes, it's important to build with "-fsigned-char" on ARM...

Bingo !

Thanks everyone for the help.