common, vo_opengl: add/use helper for formatted strings on the stack

Seems like I really like this C99 idiom. No reason not to generalize it
do snprintf(). Introduce mp_tprintf(), which basically this idiom to
snprintf(). This macro looks like it returns a string that was allocated
with alloca() on the caller site, except it's portable C99/C11. (And
unlike alloca(), the result is valid only within block scope.)

Use it in 2 places in the vo_opengl code. But it has the potential to
make a whole bunch of weird looking code look slightly nicer.

1 files changed, 1 insertions, 2 deletions

diff --git a/video/out/opengl/utils.c b/video/out/opengl/utils.c
index f5c639d98d..2624ad7715 100644
--- a/video/out/opengl/utils.c
+++ b/video/out/opengl/utils.c
@@ -919,8 +919,7 @@ static GLuint compile_program(struct gl_shader_cache *sc, const char *vertex,
     compile_attach_shader(sc, prog, GL_VERTEX_SHADER, vertex);
     compile_attach_shader(sc, prog, GL_FRAGMENT_SHADER, frag);
     for (int n = 0; sc->vertex_entries[n].name; n++) {
-        char vname[80];
-        snprintf(vname, sizeof(vname), "vertex_%s", sc->vertex_entries[n].name);
+        char *vname = mp_tprintf(80, "vertex_%s", sc->vertex_entries[n].name);
         gl->BindAttribLocation(prog, n, vname);
     }
     link_shader(sc, prog);