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    <p><strong>NEW ANSWER </strong>:</p> <p>In my original answer (below), I had to have two different macros to support assertions in a function scope and at the global scope. I wondered if it was possible to come up with a single solution that would work in both scopes.</p> <p>I was able to find a solution that worked for Visual Studio and Comeau compilers using extern character arrays. But I was able to find a more complex solution that works for GCC. But GCC's solution doesn't work for Visual Studio. :( But adding a '#ifdef __ GNUC __', it's easy to choose the right set of macros for a given compiler.</p> <p><strong>Solution:</strong></p> <pre><code>#ifdef __GNUC__ #define STATIC_ASSERT_HELPER(expr, msg) \ (!!sizeof \ (struct { unsigned int STATIC_ASSERTION__##msg: (expr) ? 1 : -1; })) #define STATIC_ASSERT(expr, msg) \ extern int (*assert_function__(void)) [STATIC_ASSERT_HELPER(expr, msg)] #else #define STATIC_ASSERT(expr, msg) \ extern char STATIC_ASSERTION__##msg[1]; \ extern char STATIC_ASSERTION__##msg[(expr)?1:2] #endif /* #ifdef __GNUC__ */ </code></pre> <p>Here are the error messages reported for <code>STATIC_ASSERT(1==1, test_message);</code> at line 22 of test.c:</p> <p><strong>GCC:</strong></p> <pre><code>line 22: error: negative width in bit-field `STATIC_ASSERTION__test_message' </code></pre> <p><strong>Visual Studio:</strong></p> <pre><code>test.c(22) : error C2369: 'STATIC_ASSERTION__test_message' : redefinition; different subscripts test.c(22) : see declaration of 'STATIC_ASSERTION__test_message' </code></pre> <p><strong>Comeau:</strong></p> <pre><code>line 22: error: declaration is incompatible with "char STATIC_ASSERTION__test_message[1]" (declared at line 22) </code></pre> <p><p>&nbsp;<br>&nbsp;<br></p> <p><strong>ORIGINAL ANSWER </strong>:</p> <p>I do something very similar to what Checkers does. But I include a message that'll show up in many compilers:</p> <pre><code>#define STATIC_ASSERT(expr, msg) \ { \ char STATIC_ASSERTION__##msg[(expr)?1:-1]; \ (void)STATIC_ASSERTION__##msg[0]; \ } </code></pre> <p>And for doing something at the global scope (outside a function) use this:</p> <pre><code>#define GLOBAL_STATIC_ASSERT(expr, msg) \ extern char STATIC_ASSERTION__##msg[1]; \ extern char STATIC_ASSERTION__##msg[(expr)?1:2] </code></pre>
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    1. COI have something similar here: http://www.atalasoft.com/cs/blogs/stevehawley/archive/2007/10/29/disgusting-c-ism.aspx
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      1. USplinth
    2. COI like what you do with the msg parameter; I may have to add that capability to mine. I'll also have to test mine on gcc. I wonder if you changed the '2' to a '-1' in your conditional char array declaration, wouldn't that have to cause an error on gcc? Then you could get rid of the gcc special case.
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      1. USMichael Burr
 

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