Bug 514748

Summary:

Spurious 'array subscript is above array bounds' warning.

Product:

[Fedora] Fedora

Reporter:

David Woodhouse <dwmw2>

Component:

gcc

Assignee:

Jakub Jelinek <jakub>

Status:

CLOSED UPSTREAM

QA Contact:

Fedora Extras Quality Assurance <extras-qa>

Severity:

medium

Docs Contact:

Priority:

low

Version:

CC:

chemobejk, jakub

Target Milestone:

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Target Release:

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Hardware:

powerpc

OS:

Linux

Whiteboard:

Fixed In Version:

Doc Type:

Bug Fix

Doc Text:

Story Points:

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Clone Of:

Environment:

Last Closed:

2009-08-03 08:32:35 UTC

Type:

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Regression:

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Documentation:

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CRM:

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Category:

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oVirt Team:

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RHEL 7.3 requirements from Atomic Host:

Cloudforms Team:

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Target Upstream Version:

Embargoed:

Attachments:

Description	Flags
test case	none

Description David Woodhouse 2009-07-30 15:57:07 UTC

See bug #505071.

Attached preprocessed source fails to build with -Wall -Werror -O2:

pmac /home/dwmw2 $ gcc -c -o sip-sec-ntlm.o sip-sec-ntlm.i  -Wall  -Werror -O2
cc1: warnings being treated as errors
sip-sec-ntlm.c: In function ‘purple_ntlm_gen_authenticate’:
sip-sec-ntlm.c:509: error: array subscript is above array bounds

gcc version 4.4.0 20090506 (Red Hat 4.4.0-4) (GCC) 

As observed in bug #505071, phrasing the pointer arithmetic slightly differently makes it work fine. The three commented out versions build OK:

	tmsg->dom_off = sizeof(struct authenticate_message);

 	tmp = ((char*) tmsg) + tmsg->dom_off;
//	tmp = ((char*) tmsg) + sizeof(struct authenticate_message);
//	tmp = (char *) (tmsg+1);
//	tmp = (char *)&tmsg[1];

Comment 1 David Woodhouse 2009-07-30 15:57:34 UTC

Sorry, that should be bug #512170

Comment 2 Stefan Becker 2009-07-30 17:14:04 UTC

David: You forgot to add the pre-processed file...

Comment 3 David Woodhouse 2009-07-30 17:28:04 UTC

Created attachment 355708 [details]
test case

Comment 4 Stefan Becker 2009-08-02 16:34:16 UTC

FYI: looks like this is not a ppc architecture bug. arm-unknown-linux-gnueabi on Ubuntu reports the same error:

 <https://launchpad.net/ubuntu/+source/pidgin-sipe/1.5.0-0ubuntu1>
 <http://launchpadlibrarian.net/29699481/buildlog_ubuntu-karmic-armel.pidgin-sipe_1.5.0-0ubuntu1_FAILEDTOBUILD.txt.gz>

cc1: warnings being treated as errors
sip-sec-ntlm.c: In function 'sip_sec_init_sec_context__ntlm':
sip-sec-ntlm.c:507: error: array subscript is above array bounds
make[2]: *** [libsipe_la-sip-sec-ntlm.lo] Error 1

Comment 5 Jakub Jelinek 2009-08-03 07:43:45 UTC

Simplified testcase:
struct A
{
  unsigned char a1[8];
  unsigned short a2, a3, a4, a5, a6, a7;
};

int bar (void *, const char *, int);
char *foo (void *, int);

char *
baz (const char *x, const char *y)
{
  int a = sizeof (struct A) + 2 * (__builtin_strlen (y)
				   + __builtin_strlen (x) + 24) + 16;
  struct A *b = __builtin_malloc (a);
  char *c;
  int d;

  b->a4 = sizeof (struct A);
  c = ((char *) b) + b->a4;
  d = ((char *) b) + a - c;
  b->a2 = b->a3 = (unsigned short) bar (c, y, d);
  c += b->a2;
  d = ((char *) b) + a - c;
  b->a7 = b->a4 + b->a2;
  b->a5 = b->a6 = (unsigned short) bar (c, x, d);
  c = foo (b, a);
  return c;
}

Comment 6 Jakub Jelinek 2009-08-03 08:32:35 UTC

Tracking upstream.  As a workaround, either use one of the above mentioned workarounds, or make sure the first field in the struct isn't a char array.

Comment 7 David Woodhouse 2009-08-03 08:51:53 UTC

If you drop the 'unsigned' and use just 'char a1[8]' in your test case, in the definition of 'struct A', then it'll occur on architectures where 'char' is signed by default too.