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POTypecasting (or deference) void * to struct foo*
 

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    <p>In api.h</p> <pre><code>typedef void* hidden_my_type; void do_something(my_type x); </code></pre> <p>In core.c</p> <pre><code>struct _my_type { int a; } void do_something(hidden_my_type void_x) { struct *_my_type x = void_x; /*Don't understand is that correct way to do, as I'm getting segmentation fault error */ printf("Value: %d\n", x-&gt;a); } </code></pre> <p>Other way I thought as,</p> <pre><code>struct *_my_type x = (struct _my_type *)malloc(sizeof(struct _my_type)); void_x = x printf(Value: %d\n", x-&gt;a); </code></pre> <p>But still I'm getting seg-fault error.</p> <hr> <p>ok here is the problem with void*....</p> <p>e.g. in core.c</p> <pre><code>void init_my_type(hidden_my_type a) { my_type *the_a = malloc(...); a = the_a // &lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt; is this correct?! a is void* and the_a // is original type pthread_cond_init(&amp;the_a-&gt;...); .. (in short any other methods for init ..) } void my_type_destroy(my_hidden_type x) { my_type *the_x = x; pthread_detroy(&amp;the_x-&gt; ...); } </code></pre> <p>in main.c</p> <pre><code>test() { my_hidden_type x; init_my_type(x); .... my_type_detroy(x); } </code></pre> <p>this it self should fail. as in main.c test function, x is void* ... init will allocate but in destroy I'm again passing void* .. which can be anything!</p> <p>EDIT (Solved for me)</p> <p>In api.h</p> <pre><code>typedef void* hidden_my_type; void do_something(my_type x); </code></pre> <p>In core.c</p> <pre><code> struct _my_type { int a; } void init_hidden_type(hidden_my_type void_p_my_type) { struct _my_type *real_my_type = (struct _my_type *)malloc(sizeof(struct _my_type)); //--- Do init for your type --- void_p_my_type = real_my_type; } void do_something(hidden_my_type void_x) { struct *_my_type x = void_x; printf("Value: %d\n", x-&gt;a); } </code></pre>
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    1. COPlease show your *actual* code, not re-written code (I can tell this isn't your real code because it couldn't possibly compile).
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      1. USOliver Charlesworth
    2. COAlso, don't hide pointers inside typedefs; it's confusing!
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      1. USOliver Charlesworth
    3. COwell my actual code is similar to this .. I can't upload that!!! and for Opaque type reason I'm using void* ... its confusing but need to do! :(
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