Ramkumar Ramachandra wrote on Thu, Sep 23, 2010 at 01:12:52 +0530: > Daniel Shahaf writes: > > Choosing path=NULL to represent "the root" seems odd to me (that's not > > how we usually represent it), but that's for another day. > > I think I'm using "" to represent the root somewhere, but I'll have to > check this. I'll figure something out during the cleanup. >
I see. > > > True. However, abspath is a `char *` with no memory allocated to it: I > > > want whatever its value is to be allocated in `pool` since it's passed > > > around. > > > > I think you've got your pointers confused. Can you drop the pstrdup(), > > see that nothing breaks, and then we can discuss why nothing broke? > > Hehe, I wouldn't be surprised if this is the case -- I've been working > with APR pools day and night now :p > > Okay, I'll drop this during the cleanup. Do explain this to me though :) abspath is a pointer, lives on the stack, and is passed by value (like any old int) in function calls. What you allocate from the pool is the value it points to --- i.e., the two bytes of "/". However, literal string constants are static strings --- they are loaded into memory from the binary image (ever tried 'strings /usr/bin/svn'?) and stay there until that is unloaded --- while pool-allocated strings allocated on the heap, and stays there until the pool is cleared. The other difference is that literal strings are not writable (they are const char *) while pool-allocate strings are mutable (non-const char *). So, the only reasons you'd have to duplicate a static string is if the static string lives in a library which you know you'll unload[1] or if you need a non-const char * for some reason. In your case, 'abspath' is a const char *, so neither of these cases applies. Okay? Daniel (waiting to hear from you that dropping the strdup() causes a segfault) [1] Thanks, dev@ archives.
