Messages in this thread | | | Date | Mon, 13 Jan 2003 16:01:32 -0500 (EST) | From | "Richard B. Johnson" <> | Subject | Re: [PATCH] Make `obsolete params' work correctly if MODULE_SYMBOL_PRE |
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On Mon, 13 Jan 2003 Valdis.Kletnieks@vt.edu wrote:
> On Mon, 13 Jan 2003 15:28:45 EST, "Richard B. Johnson" said: > > > void foo(int len) > > { > > char use[0x100]; > > char bar[len]; > > } > > > > In the case of 'use', the compiler subtracts (0x100 * sizeof(char)) > > from the current stack value and uses that as the location for 'use'. > > In the case of 'bar' the compiler subtracts (len * sizeof(char)) > > from the current stack value and uses that as the location for 'bar'. > > One or the other of these is missing a -0x100 for the location... > > void foo (int len1, unsigned int len2) > { > char bar[0x100]; > char baz[len1]; > char quux[len2]; > char moby[8]; > } > > And moby[6] is *where*? ;) Bonus points for getting this right if > compiled with -fvomit-stack-pointer. <evil grin> ;) > --
Trivial. The constant stuff gets allocated first, then the dynamic. You can write the code in any order you want, but the code generation is as though you did: char bar [0x100]; char moby[8]; Also, vomit-stack-pointer is "f(v)omit-frame-pointer". It works the same. No problem except when trying to find local variables in the debugger (known -g implimentation "feature"). The frame pointer is BP. The stack is never omitted. You can save a few instructions if you don't use it.
Cheers, Dick Johnson Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips). Why is the government concerned about the lunatic fringe? Think about it.
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