Looks great to me.
Reviewed-by: Roland Scheidegger <srol...@vmware.com>
Am 24.09.2018 um 17:19 schrieb Emil Velikov:
> This reverts commit 3d81e11b49366b5636b8524ba0f8c7076e3fdf34.
>
> As reported by Federico, some games require the 'sort by year' since
> they truncate the extensions which do not fit the fixed size string
> array.
>
> Seemingly I did not consider that as the documentation (both Mesa and
> Nvidia) mention about program crashes ... which are worked around by
> setting the env. variable.
>
> This commit reinstates the workaround and enhances the documentation.
>
> Cc: Federico Dossena <i...@fdossena.com>
> Cc: Timothy Arceri <tarc...@itsqueeze.com>
> Cc: Marek Olšák <mar...@gmail.com>
> Cc: Roland Scheidegger <srol...@vmware.com>
> Cc: Ian Romanick <i...@freedesktop.org>
> Reported-by: Federico Dossena <i...@fdossena.com>
> Fixes: 3d81e11b493 ("mesa: remove unnecessary 'sort by year' for the GL
> extensions")
> ---
> UNTESTED: Resolved the revert conflicts, but I haven't done any actual
> testing. If Federico can do the honours that'll be amazing.
>
> src/mesa/main/extensions.c | 46 ++++++++++++++++++++++++++++++++++++--
> 1 file changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/main/extensions.c b/src/mesa/main/extensions.c
> index 25c3161f7d0..4d95a072793 100644
> --- a/src/mesa/main/extensions.c
> +++ b/src/mesa/main/extensions.c
> @@ -335,6 +335,30 @@ _mesa_extension_supported(const struct gl_context *ctx,
> extension_index i)
> return (ctx->Version >= ext->version[ctx->API]) && base[ext->offset];
> }
>
> +/**
> + * Compare two entries of the extensions table. Sorts first by year,
> + * then by name.
> + *
> + * Arguments are indices into _mesa_extension_table.
> + */
> +static int
> +extension_compare(const void *p1, const void *p2)
> +{
> + extension_index i1 = * (const extension_index *) p1;
> + extension_index i2 = * (const extension_index *) p2;
> + const struct mesa_extension *e1 = &_mesa_extension_table[i1];
> + const struct mesa_extension *e2 = &_mesa_extension_table[i2];
> + int res;
> +
> + res = (int)e1->year - (int)e2->year;
> +
> + if (res == 0) {
> + res = strcmp(e1->name, e2->name);
> + }
> +
> + return res;
> +}
> +
>
> /**
> * Construct the GL_EXTENSIONS string. Called the first time that
> @@ -372,8 +396,8 @@ _mesa_make_extension_string(struct gl_context *ctx)
>
> if (i->year <= maxYear &&
> _mesa_extension_supported(ctx, k)) {
> - length += strlen(i->name) + 1; /* +1 for space */
> - extension_indices[count++] = k;
> + length += strlen(i->name) + 1; /* +1 for space */
> + ++count;
> }
> }
> for (k = 0; k < MAX_UNRECOGNIZED_EXTENSIONS; k++)
> @@ -385,6 +409,24 @@ _mesa_make_extension_string(struct gl_context *ctx)
> return NULL;
> }
>
> + /* Sort extensions in chronological order because idTech 2/3 games
> + * (e.g., Quake3 demo) store the extension list in a fixed size buffer.
> + * Some cases truncate, while others overflow the buffer. Resulting in
> + * misrendering and crashes, respectively.
> + * Address the former here, while the latter will be addressed by setting
> + * the MESA_EXTENSION_MAX_YEAR environment variable.
> + */
> + j = 0;
> + for (k = 0; k < MESA_EXTENSION_COUNT; ++k) {
> + if (_mesa_extension_table[k].year <= maxYear &&
> + _mesa_extension_supported(ctx, k)) {
> + extension_indices[j++] = k;
> + }
> + }
> + assert(j == count);
> + qsort(extension_indices, count,
> + sizeof *extension_indices, extension_compare);
> +
> /* Build the extension string.*/
> for (j = 0; j < count; ++j) {
> const struct mesa_extension *i =
> &_mesa_extension_table[extension_indices[j]];
>
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