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I'm trying to write a simple shared library that would log malloc calls to stderr (a sort of 'mtrace' if you will). However, this is not working. Here's what I do: /* mtrace.c */ #include <dlfcn.h> #include <stdio.h> static void* (*real_malloc)(size_t); void *malloc(size_t size) { void *p = NULL; fprintf(stderr, "malloc(%d) = ", size); p = real_malloc(size); fprintf(stderr, "%p\n", p); return p; } static void __mtrace_init(void) __attribute__((constructor)); static void __mtrace_init(void) { void *handle = NULL; handle = dlopen("libc.so.6", RTLD_LAZY); if (NULL == handle) { fprintf(stderr, "Error in `dlopen`: %s\n", dlerror()); return; } real_malloc = dlsym(handle, "malloc"); if (NULL == real_malloc) { fprintf(stderr, "Error in `dlsym`: %s\n", dlerror()); return; } } I compile this with: gcc -shared -fPIC -o mtrace.so mtrace.c And then when I try to execute ls : $ LD_PRELOAD=./mtrace.so ls malloc(352) = Segmentation fault Now, I suspect that dlopen needs malloc, and as I am redefining it within the shared library, it uses that version with the still unassigned real_malloc . The question is...how do I make it work? P.S. sorry for the paucity in tags, I couldn't find appropriate tags, and I still don't have enough reputation to create new ones.

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