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    <p>You can do this by generating a large header file, e.g. using a little bit of Python:</p> <pre class="lang-py prettyprint-override"><code>for x in range(0,256): print '#define BODGE_0x%x \\x%x' % (x,x) </code></pre> <p>And then use the output of that in C:</p> <pre><code>#include &lt;stdio.h&gt; #include "bodge.h" #define xstr(s) str(s) #define str(s) #s #define XCHR(x,y) (xstr(x##y)) #define CHR(x) xstr(BODGE_##x) int main() { return printf("%s\n", CHR(0x20)); } </code></pre> <p>Which does exactly what you asked for, <code>gcc -E</code> shows:</p> <pre><code>return printf("%s\n", "\x20"); </code></pre> <hr> <p>It's possible (but fiddly) to do something less crude if you accept calling <code>CHR(20)</code> to imply hex without the <code>0x</code> prefix.</p> <p>The obvious solution would be to build a macro that expands to:</p> <pre><code>printf("%s", "\x" "20"); </code></pre> <p>which is fairly easy to do with one level of indirection, and the obvious assumption would be that the compile time concatenation of strings would handle this. Unfortunately that solution isn't viable because of the point in translation when the escape sequence gets handle. GCC therefore gives the error:</p> <pre><code>error: \x used with no following hex digits </code></pre> <p>We can however work around that and cause the string "\x20" to be generated by using a pre-processor concatenation (<code>##</code>) in conjunction with the "usual" preprocessor stringification indirection:</p> <pre><code>#include &lt;stdio.h&gt; #define xstr(s) str(s) #define str(s) #s #define XCHR(x,y) (xstr(x##y)) #define CHR(y) XCHR(\x,y) int main() { return printf("%s", CHR(20)); } </code></pre> <p>This does work and, gcc -E shows:</p> <pre><code>return printf("%s", ("\x20")); </code></pre> <p>which is what we'd hope to see when the macro works.</p> <hr> <p>You could also do:</p> <pre><code>#define CHR(x) ((char[2]){(x), 0x0}) </code></pre> <p>which has the desired effect.</p>
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    1. POConstruct string/char escape sequence using C macro
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    1. POConstruct string/char escape sequence using C macro
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    1. COOf course having said all that it looks like you're trying to solve the wrong problem the wrong way. There's got to be a neater solution to whatever your real problem is.
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    2. COGenius! Get that, C preprocessor! ;-) I thought about (ab)using C99 compound literals, but that definitely didn't work, because what I actually need to do is: "#define LSTR(s) CHR(sizeof(s)-1) s || intern_str(LSTR("foo"));", i.e. need to have string, and static string, defined in the end. Yeah, neater solution would be to use C++11's constexpr's (especially because I also need to put hash in there), but people don't want to use C++11, sticking with ancient C, go figure...
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    3. COBut yeah, C preprocessor doesn't do sizeof(), so LSTR() macro from previous comment wouldn't work. Anyway, the original question as it is answered well. Gotta write custom preprocessor for real case though...
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