[Mesa-dev] gallium state tracker calls calloc for 0 sizes arrays ?

[Hans de Goede]

Hi All,

While debugging: https://bugzilla.redhat.com/show_bug.cgi?id=1008089

I made a apitrace recording of the a single slide transition
animation, and since I suspected memory corruption replayed
it using ElectrFence + glretrace, this finds a 0 sized array
allocation at src/mesa/state_tracker/st_glsl_to_tgsi.cpp: 5565:

    if (proginfo->Parameters) {
       t->constants = (struct ureg_src *)
          calloc(proginfo->Parameters->NumParameters, sizeof(t->constants[0]));

And if I protect the code against that one, another one at 5618:

    t->immediates = (struct ureg_src *)
       calloc(program->num_immediates, sizeof(struct ureg_src));

With the regular glibc malloc these both succeed as it actually
returns a valid memory address (posix says it may also return NULL)

I believe that the fragment program in question comes from:

src/mesa/main/state.c update_program() and then from the

    else if (ctx->FragmentProgram._MaintainTexEnvProgram) {
       /* Use fragment program generated from fixed-function state */

    }

block.

Interestingly enough if I allow malloc(0) to proceed from ElectricFence,
then the glretrace runs fine, and even renders correctly, where as
running the same gl command stream from libreoffice impress leads
to missrendering on nv3c.

So 2 questions:

1) Is it normal / expected for st_translate_program() to get called
with an empty but not NULL proginfo->Parameters resp. num_immediates == 0 ?

If not where would I begin to look for finding the culprit of this ?


2) Since the glretrace does work outside of libreoffice impress, I think
it may have something to do with the visual chosen by libreoffice impress,
is there an easy way to find out what visual lo is choosing?

Regards,

Hans