On Fri, Feb 20, 2009 at 7:48 PM, tom fogal <tfo...@alumni.unh.edu> wrote:
> There is an issue loading mangled mesa symbols.
>
> In _glapi_get_proc_address, there is the code:
>
> #ifdef MANGLE
> if (funcName[0] != 'm' || funcName[1] != 'g' || funcName[2] != 'l')
> return NULL;
> #else
> if (funcName[0] != 'g' || funcName[1] != 'l')
> return NULL;
> #endif
>
> thus, if the user is mangling mesa, any string they give which does not
> have the mangled name will quickly return NULL. Sure, fine, but then
> eventually `find_entry' will be called for some paths, which contains
> the code:
>
> for(i from 1 to N...) {
> const char *testName = gl_string_table + static_functions[i].Name_offset;
> if (strcmp(testName, n) == 0) {
> return &static_functions[i];
> }
> }
>
> Unfortunately the static_functions table only contains the demangled
> names. Thus, the user *cannot* load functions from a mangled mesa
> library: if they use the non-mangled name, then the #ifdef in
> _glapi_get_proc_address will bail on them without even searching; if
> they use the mangled name, find_entry will iterate through the entire
> table and never find a match because the table only contains the
> non-mangled name.
>
> I have verified that removing the `#ifdef MANGLE' case and simply
> using the else clause allows the user to load basic functions, e.g.
> `glBegin'. Of course, this means that a user must load `glBegin'
> instead of `mglBegin' regardless of whether or not they are using
> mangled Mesa.
>
> I'm not really sure if that's a good thing or a bad thing, but I'll let
> you decide. Please inform me which of these solutions you'd like to
> see:
>
> 1. Remove the #ifdef MANGLE case. To load `glBegin', for example,
> users must call `mglXGetProcAddress("glBegin")'. [1]
> 2. use an #ifdef MANGLE case in find_entry to dynamically build a
> string which is essentially ("m" concat gl_string_table +
> static_functions[i].Name_offset). Do the comparison based on
> the dynamic string and the argument.
> 3. Change the table such that it contains `glBegin' (etc.) in the
> unmangled case, and `mglBegin' in the mangled case.
> 4. other that I haven't thought of (please explain)
I opted for #2 by just skipping the 'm' prefix for the mangled case.
There's some other strcmp() calls that may need updating too. Maybe
you could follow-up with patches if more changes are needed.
Updated code in git (plus your other two issues).
-Brian
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