[GRASS-dev] strange for loop bug

[Yann Chemin]

Hello,

I am writing a raster module for image processing, and the
for(col=0;col<ncols;col++) loop behaves strangely (segfault), the
number of lines of code inside is 239 lines. If i reduce the number of
functions inside to a simple copy of an input raster, the number of
line being 15 less, then it does not seg fault.

The error is basically the variable col becoming a very large negative
number, which is constant for a compilation, may not be the same
actually in all modifications of the code tested.

The interesting thing is that it processes through 77 rows of Null
pixels (sending outrast[col] to G_set_d_null_value(..)) and when it
comes to the first real data processing, it gives the output value to
outrast[col], goes up the loop and at that moment, col passes from
1450 to -2085319823.

Anybody has any experience of similar event?
Any idea what could corrupt a for() loop variable?

I am also going to change gcc version in case it is a gcc bug.

Thank you,
Yann