title: Precompiled headers and compiling universal objects on OSX
body: <p>We are using precompiled headers with GCC for our project and build them like this:</p>
  
  <pre><code>gcc $(CFLAGS) precompiledcommonlib.h
  </code></pre>
  
  <p>Now I'm building the project on OSX 10.6 and trying to use the nifty feature of building for all architectures at the same time like this:</p>
  
  <pre><code>gcc $(CFLAGS) -c -arch i386 -arch x86_64 commonlib.c  
  </code></pre>
  
  <p>However, it seems this does not work for the precompiled headers:</p>
  
  <pre><code>gcc $(CFLAGS) -arch i386 -arch x86_64 precompiledcommonlib.h
  Undefined symbols for architecture i386:
    "_main", referenced from:
        start in crt1.10.6.o
  ld: symbol(s) not found for architecture i386
  collect2: ld returned 1 exit status
  Undefined symbols for architecture x86_64:
    "_main", referenced from:
        start in crt1.10.6.o
  ld: symbol(s) not found for architecture x86_64
  collect2: ld returned 1 exit status
  lipo: can't open input file: /var/folders/z1/z1A0sPkqGDyPrZWo9ysVK++++TI/-Tmp-//cc3W2gwd.out (No such file or directory)
  </code></pre>
  
  <p>Edit:
  As Mark pointed out as per XCode the precompiled header has to be built separately for each architecture, so my question is rather if there is any way to have gcc use the right precompiled header when building universal objects.</p>
  
  <p>I do realise that I could build each architecture completely separate like XCode does it but I would much rather take advantage of the possibility to build them at the same time and not have to mess around with different build configurations.</p>