Re: Brain fart alert

[Arnaldo Carvalho de Melo <acme-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>]

Em Mon, Aug 20, 2012 at 03:02:16PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Sat, Jul 21, 2012 at 08:22:33PM +0200, Nicolas escreveu:
> > I tried using pahole, but I get a brain fart alert with the file
> > attached (which is an extract from stdio.h). I'm running dwarves 1.10,
> > libdw1 0.152 and g++ 4.6.1, on i386.
> > 
> > Here is what I get:
> > 
> > $ g++ -Wall -g -c brainfart.cpp -o brainfart.o && pahole brainfart.o
> > class ios_base {
> > 	enum _Ios_Openmodeconst    in;                   /*     0     4 */
> > 	typedef enum _Ios_Fmtflags fmtflags;
> > 
> > 	/* size: 1, cachelines: 1, members: 1 */
> > 	/* padding: 65533 */
> > 	/* last cacheline: 1 bytes */
> > 
> > 	/* BRAIN FART ALERT! 1 != 4 + 0(holes), diff = -3 */
> 
> Can you please clone my git tree and try it from there?
> 
> git clone git://git.kernel.org/pub/scm/devel/pahole/pahole
> cd pahole
> mkdir build
> cd build
> cmake ..
> cd ..
> make -C build
> build/pahole brainfart.o
> 
> Now I'm getting:
> 
> [acme@sandy pahole]$ build/pahole brainfart.o 
> class ios_base {
> 	static enum _Ios_Openmodeconst    in = 8;        /*     0     0 */
> 	typedef enum _Ios_Fmtflags fmtflags;
> 
> 
> 	/* size: 1, cachelines: 0, members: 0, static members: 1 */
> 	/* last cacheline: 1 bytes */
> };
> [acme@sandy pahole]$
> 
> I still need to get the 'const' there, from the fact that it has a
> DW_AT_const_value, that is already captured, just forgot to add the
> 'const' there, will do after some errands here.
> 
> Also I'll check that the member type is an enum, will lookup the
> enumerator entry that has the DW_AT_const_value and replace that '8'
> with it.

I also noticed that there is a problem when the static member is not the
first, related to bitfield hole detection, will fix it too.

- Arnaldo
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