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Groups > comp.lang.c > #138231
| From | Anton Shepelev <anton.txt@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] |
| Date | 2018-11-25 14:19 +0300 |
| Organization | A noiseless patient Spider |
| Message-ID | <20181125141906.7147e2a5008868b3cbec6ca7@gmail.com> (permalink) |
| References | (1 earlier) <20181119022614.5cf93af72a29cb41cdc86910@gmail.com> <20181124192405.870012f12c0ac1c1dc8777d8@gmail.com> <87d0qu2mdb.fsf@bsb.me.uk> <20181125011237.7345a0c1c8b26130000e9c2f@gmail.com> <87va4mylze.fsf@bsb.me.uk> |
Ben Bacarisse to Anton Shepelev:
> > Ben Bacarisse to Anton Shepelev:
> >
> > > > This is the third edition of my dynamic array
> > > > implementation.
> > >
> > > It looks overly complicated to me. valgrind reports a
> > > bug ->
> >
> > I failed to interpret its output. It shows several
> > errors of the form:
> >
> > Invalid write of size 2
> > ==20399== at 0x4C2D98B: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_me
> > ==20399== by 0x400938: da_add (in /home/a/antonius/programs/wcm2/datest)
> >
> > I am not even sure they indicate bugs. I have
> > explicitly test that in da_add memcpy receives 4 in its
> > third argument.
>
> There really is a problem. If I print the address being
> written to by the memcpy in da_add it lies just outside
> the storage most recently allocated:
>
> realloc((nil), 4 * 1 + 16 = 20) = 0x58fdc80 ... 0x58fdc94
> realloc(0x58fdc80, 4 * 2 + 16 = 24) = 0x58fe120 ... 0x58fe138
> realloc(0x58fe120, 4 * 4 + 16 = 32) = 0x58fe180 ... 0x58fe1a0
> memcpy(0x58fe1a0, 0x1fff000208, 4)
>
> (These are from inserted printf statements.)
>
> As you can see, the most recent allocation is for 32 bytes
> from 0x58fe180 to 0x58fe1a0 and the memcpy starts just
> outside that block.
Thank you! It was a genuine off-by-one error in the
function for adding an empty element.
#include <stdlib.h>
#include <string.h>
#include "dynarray.h"
/* ----------------------------- Dynamic array ---------------------------------
Memory layout:
|<------ OFS ------>|
[dynarray_t][padding][data...]
*/
struct dynarray_t /* the internal data of the dynamic array */
{ unsigned int capacity; /* always a power of two */
unsigned int length; /* number of elements in the array */
unsigned short size; /* size of an array element */
};
#define SH_OR(x, n) ((x) | (x) >> (n))
static int OFS =
SH_OR(SH_OR(SH_OR(SH_OR( sizeof( struct dynarray_t ) -1, 1), 2), 4), 8) + 1;
#define META(a) ((struct dynarray_t*)((char*)(a) - OFS))
/* Round a number up to the next power of two: */
static unsigned pow2up( unsigned v )
{ unsigned res;
res = 1;
while( res < v )
{ res = res << 1; }
return res;
}
/* Adjust array to accomodate a new capacity. */
/* Upon failure, frees the array and returns NULL. */
static struct dynarray_t * adjust
( struct dynarray_t * da, unsigned short size, unsigned cap )
{ struct dynarray_t * da2;
da2 = realloc( da, size * cap + OFS );
if( da2 == NULL ) free( da );
else da2->capacity = cap;
return da2;
}
/* ------------ Operations on a dynamic array (public functions) ------------ */
void* da_newl( size_t size, unsigned int len )
{ void *a;
struct dynarray_t *da;
a = NULL;
da = adjust( NULL, size, pow2up( len ) );
if( da != NULL )
{ da->size = size;
da->length = len;
a = (char*)da + OFS;
}
return a;
}
void* da_new( size_t size )
{ return da_newl( size, 0 ); }
void* da_setlen( void * a, int len )
{ unsigned int newcap;
struct dynarray_t *da;
da = META( a );
da->length = len;
newcap = pow2up( len );
if( da->capacity != newcap )
{ da = adjust( da, da->size, newcap );
if( da != NULL ) a = (char*)da + OFS;
else a = NULL;
}
return a;
}
void* addemp( struct dynarray_t* da, void ** data )
{ void* a;
unsigned dataofs;
a = NULL;
dataofs = da->size * da->length;
da->length++;
if( da->length > da->capacity )
{ da->capacity <<= 1;
da = adjust( da, da->size, da->capacity );
}
if( da != NULL )
{ a = (char*)da + OFS;
*data = (char*)a + dataofs;
}
return a;
}
void* da_addemp( void * a, void ** data )
{ return addemp( META( a ), data ); }
void* da_add( void * a, void * data )
{ unsigned int size;
void* addr;
struct dynarray_t *da;
da = META(a);
size = da->size;
a = addemp( da, &addr );
if( a != NULL ) memcpy( addr, data, size );
return a;
}
void da_free( void * a )
{ free( META( a ) ); }
int da_len( void * a )
{ return META( a )->length; }
--
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Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-17 14:38 +0300
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-17 17:37 +0300
Re: Pointer conversion and alignment Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-17 21:01 +0000
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 00:43 +0300
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 01:20 +0300
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-17 18:12 -0500
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 02:32 +0300
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-17 18:59 -0500
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 12:40 +0300
Re: Pointer conversion and alignment Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-18 02:14 +0000
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 13:23 +0300
Re: Pointer conversion and alignment Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-18 11:28 +0000
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 15:31 +0300
Re: Pointer conversion and alignment Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-18 15:03 +0000
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 23:00 +0300
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 00:49 +0300
Re: Pointer conversion and alignment Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-11-17 06:52 -0800
Re: Pointer conversion and alignment Ian Collins <ian-news@hotmail.com> - 2018-11-18 09:18 +1300
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-11-17 13:49 -0800
Re: Pointer conversion and alignment Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-11-17 13:57 -0800
Re: Pointer conversion and alignment Ian Collins <ian-news@hotmail.com> - 2018-11-18 11:08 +1300
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 01:13 +0300
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-11-17 18:37 -0800
Re: Pointer conversion and alignment Philipp Klaus Krause <pkk@spth.de> - 2018-11-18 14:14 +0100
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-17 10:05 -0500
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 01:08 +0300
Re: Pointer conversion and alignment "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-11-17 14:31 -0800
Re: Pointer conversion and alignment "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-11-17 16:10 -0800
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-18 15:01 +0300
Re: Pointer conversion and alignment James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-11-18 07:25 -0500
Re: Pointer conversion and alignment "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-11-19 21:30 -0800
Re: Pointer conversion and alignment "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-11-20 14:20 -0800
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-17 18:04 -0500
Re: Pointer conversion and alignment Philipp Klaus Krause <pkk@spth.de> - 2018-11-18 14:18 +0100
Re: Pointer conversion and alignment scott@slp53.sl.home (Scott Lurndal) - 2018-11-18 19:49 +0000
Re: Pointer conversion and alignment Tim Rentsch <txr@alumni.caltech.edu> - 2018-11-23 18:27 -0800
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-23 21:59 -0500
Re: Pointer conversion and alignment Tim Rentsch <txr@alumni.caltech.edu> - 2018-11-24 00:32 -0800
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-24 08:17 -0500
Re: Pointer conversion and alignment Tim Rentsch <txr@alumni.caltech.edu> - 2018-11-29 09:55 -0800
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-29 21:48 -0500
Re: Pointer conversion and alignment Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-05 04:14 -0800
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-12-05 08:14 -0500
Re: Pointer conversion and alignment Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-05 05:29 -0800
Re: Pointer conversion and alignment David Brown <david.brown@hesbynett.no> - 2018-12-05 14:44 +0100
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-12-05 21:58 -0500
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-12-05 16:38 +0300
Re: Pointer conversion and alignment scott@slp53.sl.home (Scott Lurndal) - 2018-12-05 14:23 +0000
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-12-05 14:35 -0800
Re: Pointer conversion and alignment Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-08 19:28 -0800
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-12-09 08:18 -0500
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-12-09 14:35 -0500
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-12-09 14:04 -0800
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-12-09 20:40 -0500
Re: Pointer conversion and alignment Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-17 07:18 -0800
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-12-17 12:35 -0800
Re: Pointer conversion and alignment Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-17 12:48 -0800
Re: Pointer conversion and alignment "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-11-24 18:33 -0800
My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-19 02:26 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-19 11:08 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-19 15:37 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-19 15:39 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-19 15:07 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-19 22:24 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jameskuyper@alumni.caltech.edu - 2018-11-19 12:33 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-20 00:34 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jameskuyper@alumni.caltech.edu - 2018-11-19 14:38 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-20 00:43 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-11-19 21:44 -0500
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jadill33@gmail.com - 2018-11-20 07:11 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] bart4858@gmail.com - 2018-11-20 10:02 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-19 22:20 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-20 14:01 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Melzzzzz <Melzzzzz@zzzzz.com> - 2018-11-20 11:07 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-20 15:12 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-11-20 08:15 -0500
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-20 23:08 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jameskuyper@alumni.caltech.edu - 2018-11-20 14:13 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-21 16:38 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-11-21 09:05 -0500
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-21 20:28 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jameskuyper@alumni.caltech.edu - 2018-11-21 12:58 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-22 01:47 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jameskuyper@alumni.caltech.edu - 2018-11-21 15:50 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-24 19:37 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-21 21:22 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-21 01:15 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-19 15:06 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] mark.bluemel@gmail.com - 2018-11-19 08:05 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] scott@slp53.sl.home (Scott Lurndal) - 2018-11-19 16:49 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jameskuyper@alumni.caltech.edu - 2018-11-19 10:35 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-20 00:45 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jameskuyper@alumni.caltech.edu - 2018-11-19 14:24 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-20 15:05 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-11-20 08:31 -0500
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Richard Damon <Richard@Damon-Family.org> - 2018-11-20 20:02 -0500
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-21 22:47 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] jameskuyper@alumni.caltech.edu - 2018-11-21 13:08 -0800
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-22 00:31 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-21 21:36 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-19 16:04 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-19 14:56 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-24 19:24 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-24 21:31 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-24 21:46 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-25 01:12 +0300
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-11-25 01:39 +0000
Re: My dynamic arrays module [was:Re: Pointer conversion and alignment] Anton Shepelev <anton.txt@gmail.com> - 2018-11-25 14:19 +0300
Re: Pointer conversion and alignment jadill33@gmail.com - 2018-11-19 08:44 -0800
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-20 00:02 +0300
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-11-19 13:51 -0800
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-20 01:08 +0300
Re: Pointer conversion and alignment jameskuyper@alumni.caltech.edu - 2018-11-19 14:31 -0800
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-20 15:21 +0300
Re: Pointer conversion and alignment James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-11-20 08:59 -0500
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-11-20 11:06 -0800
Re: Pointer conversion and alignment jameskuyper@alumni.caltech.edu - 2018-11-20 12:43 -0800
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-11-20 14:33 -0800
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-21 14:33 +0300
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-21 07:49 -0500
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-11-21 12:42 -0800
Re: Pointer conversion and alignment James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-11-21 08:41 -0500
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-25 15:06 +0300
Re: Pointer conversion and alignment James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-11-25 10:47 -0500
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@g{oogle}mail.com> - 2018-11-26 12:42 +0300
Re: Pointer conversion and alignment Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-11-26 03:07 -0800
Re: Pointer conversion and alignment Keith Thompson <kst-u@mib.org> - 2018-11-26 12:56 -0800
Re: Pointer conversion and alignment Richard Damon <Richard@Damon-Family.org> - 2018-11-26 18:17 -0500
Re: Pointer conversion and alignment jameskuyper@alumni.caltech.edu - 2018-11-26 09:06 -0800
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-26 23:52 +0300
Re: Pointer conversion and alignment jameskuyper@alumni.caltech.edu - 2018-11-26 13:13 -0800
Re: Pointer conversion and alignment Anton Shepelev <anton.txt@gmail.com> - 2018-11-27 00:31 +0300
Re: Pointer conversion and alignment jameskuyper@alumni.caltech.edu - 2018-11-26 14:15 -0800
Re: Pointer conversion and alignment jadill33@gmail.com - 2018-11-19 14:33 -0800
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