Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>You can do wrapper and "overwrite" function with LD_PRELOAD - similarly to example shown earlier.</p> <pre><code>LD_PRELOAD=/path.../lib_fake_malloc.so ./app </code></pre> <p>But I recommend to do this "slightly" smarter, I mean <strong>calling dlsym once</strong>.</p> <pre><code>#define _GNU_SOURCE #include &lt;stdio.h&gt; #include &lt;stdint.h&gt; #include &lt;dlfcn.h&gt; void* malloc(size_t size) { static void* (*real_malloc)(size_t) = NULL; if (!real_malloc) real_malloc = dlsym(RTLD_NEXT, "malloc"); void *p = real_malloc(size); fprintf(stderr, "malloc(%d) = %p\n", size, p); return p; } </code></pre> <p>example I've found here: <a href="http://www.jayconrod.com/cgi/view_post.py?23" rel="noreferrer">http://www.jayconrod.com/cgi/view_post.py?23</a> post by Jay Conrod.</p> <p>But what I've found really cool at this page is that: <strong>GNU linker provides</strong> a useful option, <strong>--wrap</strong> . When I check "man ld" there is following example:</p> <pre><code>void * __wrap_malloc (size_t c) { printf ("malloc called with %zu\n", c); return __real_malloc (c); } </code></pre> <p>I agree with them that's "trivial example" :). Even dlsym is not needed. </p> <p>Let, me cite one more part of my "man ld" page:</p> <pre><code>--wrap=symbol Use a wrapper function for symbol. Any undefined reference to symbol will be resolved to "__wrap_symbol". Any undefined reference to "__real_symbol" will be resolved to symbol. </code></pre> <p>I hope, description is complete and shows how to use those things.</p>
    singulars
    1. This table or related slice is empty.
    1. POCreate a wrapper function for malloc and free in C
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USGrzegorz Wierzowiecki
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COHi I am getting error, how to resolve? ERROR: ld.so: object '/home/tmp/libjmalloc.so' from LD_PRELOAD cannot be preloaded: ignored.
      singulars
      1. PO
      1. USThangaraj
    2. COStrange. In past it worked, currently I got the same error as you. As I google it, there are many many similar cases. Please, let us know, when you find solution. I tried and couldn't - 'file' shows that binaries are same arch, so it should work. It needs more attention.
      singulars
      1. PO
      1. USGrzegorz Wierzowiecki
    3. COI had problem in two systems, in one system I corrected by replacing relative path with absolute path and in other system still digging :). I have one doubt, this method will hold good for small programs. suppose if I have a large program, then how can I find out from where (which function) the malloc function is called.
      singulars
      1. PO
      1. USThangaraj
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload