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Re: Fun with fork/exec in the XCode debugger
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Re: Fun with fork/exec in the XCode debugger


  • Subject: Re: Fun with fork/exec in the XCode debugger
  • From: Jonas Maebe <email@hidden>
  • Date: Wed, 15 Feb 2006 10:01:10 +0100


On 14 feb 2006, at 22:33, Timothy Standing wrote:

I have several functions in a statically linked library which use fork/exec to call some command line tool to perform some work. They use fork/exec and then call waitpid, WIFEXITED and WEXITSTATUS to wait for the child process to end and then retrieve its status. These calls all work fine when I run the debug build of my product by launching it in the Finder. When I run it from the XCode 2.2 debugger, however, I get results from WIFEXITED and WEXITSTATUS which don't make any sense.

Just a quick remark: if you're only forking to exec something, use vfork() instead of fork(). The performance difference is immense, because memory map copying is very expensive on Mac OS X (and the bigger the memory map is, the more expensive it becomes). I sped up compiling our compiler with itself by 25-30% by simply replacing fork with vfork in the routine which calls the assembler (which only happens 157 times in the process of compiling 150kloc divided over 157 compilation units)


On the other hand, that may confuse the debugger even more :)


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References: 
 >Fun with fork/exec in the XCode debugger (From: Timothy Standing <email@hidden>)

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