Attachment 252361 Details for Bug 464554 – LD_PRELOAD hooks for libcairo

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LD_PRELOAD hooks for libcairo

cairo-snoop.c (text/x-csrc), 1.83 KB, created by Michael Davidsaver

on 2015-04-13 19:10:12 EDT

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Filename:

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Creator: Michael Davidsaver

Created: 2015-04-13 19:10:12 EDT

Size: 1.83 KB

patch

obsolete

>#include <stdio.h>
>#include <stdlib.h>
>#include <dlfcn.h>
>
>#include <cairo/cairo.h>
>
>/*
> Can't just dlsym w/ RTLD_NEXT as libcairo
> is imported indirectly as a result of dlopen
> w/ RTLD_LOCAL, so this symbol can't found again.
>
> Instead import it again directly from libcairo,
> and hope its the same code...
>*/
>
>static void* getfn(const char *name)
>{
>  void *fn = NULL;
>  void *key = dlopen("libcairo.so", RTLD_NOW|RTLD_LOCAL);
>  if(key) {
>    char *err;
>    fn = dlsym(key, name);
>    err = dlerror();
>    if(err)
>      fprintf(stderr, "dlsym: %s\n", err);
>    else if(!fn)
>      fprintf(stderr, "no error, no symbol\n");
>    dlclose(key);
>  } else {
>    fprintf(stderr, "Failed to open libcairo\n");
>  }
>  return fn;
>}
>
>typedef void (*cairo_set_operator_t)(cairo_t *cr, cairo_operator_t op);
>
>void
>cairo_set_operator (cairo_t *cr, cairo_operator_t op)
>{
>  cairo_set_operator_t orig = (cairo_set_operator_t)getfn("cairo_set_operator");
>  fprintf(stderr, "cairo_set_operator(%p, %d)\n", cr, op);
>  if(!orig || !cr || orig==&cairo_set_operator) {
>    fprintf(stderr, "  oops! %p %p\n", orig, cr);
>    return;
>  }
>  (*orig)(cr, op);
>}
>
>typedef cairo_t * (*cairo_create_t)(cairo_surface_t *cr);
>
>cairo_t *
>cairo_create (cairo_surface_t *target)
>{
>  cairo_t *ret;
>  cairo_create_t orig = (cairo_create_t)getfn("cairo_create");
>  if(!orig || !target || orig==&cairo_create) {
>    fprintf(stderr, "  oops! %p %p\n", orig, target);
>    return NULL;
>  }
>  ret = (*orig)(target);
>  fprintf(stderr, "cairo_create(%p) = %p\n", target, ret);
>  return ret;
>}
>
>typedef void (*cairo_destroy_t)(cairo_t *cr);
>
>void
>cairo_destroy (cairo_t *cr)
>{
>  cairo_destroy_t orig = (cairo_destroy_t)getfn("cairo_destroy");
>  fprintf(stderr, "cairo_destroy(%p)\n", cr);
>  if(!orig || !cr || orig==&cairo_destroy) {
>    fprintf(stderr, "  oops! %p %p\n", orig, cr);
>    return;
>  }
>  (*orig)(cr);
>}

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Attachments on bug 464554: 252360 | 252361 | 252362