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* [Bug c/115570] New: array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]'
@ 2024-06-21 0:15 Curt.Blank at curtronics dot com
2024-06-21 0:22 ` [Bug middle-end/115570] " pinskia at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: Curt.Blank at curtronics dot com @ 2024-06-21 0:15 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115570
Bug ID: 115570
Summary: array subscript 'long unsigned int[0]' is partly
outside array bounds of 'unsigned char[4]'
Product: gcc
Version: 13.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: Curt.Blank at curtronics dot com
Target Milestone: ---
I just ran into a compile error on code that has been just fine for 18 years.
The only reason I'm compiling it is just to be sure on a new computer/Linux
install.
With gcc 4.8.3 I do not get the warnings, with gcc 13.3.0 I get the warnings
shown below the code below. The char string being converted is hex, data
returned from a solar inverter.
And like I said it's been fine and I suspect the program will run fine just
cannot fully test it yet until data collect is moved to this new server.
*--------------------------------------------------------------------------
szCvrtLong
Converts a 4 char string to a long.
----------------------------------------------------------------------------*/
unsigned long szCvrtLong(char *Buffer)
{
unsigned char cValue[4];
unsigned long *value = 0;
if (! bSwapEndian) {
cValue[0] = Buffer[aParam4] & 0xff;
cValue[1] = Buffer[aParam3] & 0xff;
cValue[2] = Buffer[aParam2] & 0xff;
cValue[3] = Buffer[aParam1] & 0xff;
} else {
cValue[0] = Buffer[aParam1] & 0xff;
cValue[1] = Buffer[aParam2] & 0xff;
cValue[2] = Buffer[aParam3] & 0xff;
cValue[3] = Buffer[aParam4] & 0xff;
}
value = (unsigned long *)cValue;
if (bVerbose) fprintf(stderr, "szCvrtLong %12lu
0x%02x%02x%02x%02x\n",*value &
0xffffffff,cValue[3],cValue[2],cValue[1],cValue[0]);
return(*value & 0xffffffff);
}
-----------
comm.c: In function 'szCvrtLong.constprop':
comm.c:1906:77: warning: array subscript 'long unsigned int[0]' is partly
outside array bounds of 'unsigned char[4]' [-Warray-bounds=]
1906 | if (bVerbose) fprintf(stderr, "szCvrtLong %12lu
0x%02x%02x%02x%02x\n",*value &
0xffffffff,cValue[3],cValue[2],cValue[1],cValue[0]);
|
^~~~~~
comm.c:1890:19: note: object 'cValue' of size 4
1890 | unsigned char cValue[4];
| ^~~~~~
comm.c:1908:12: warning: array subscript 'long unsigned int[0]' is partly
outside array bounds of 'unsigned char[4]' [-Warray-bounds=]
1908 | return(*value & 0xffffffff);
| ^~~~~~
comm.c:1890:19: note: object 'cValue' of size 4
1890 | unsigned char cValue[4];
| ^~~~~~
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/115570] array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]'
2024-06-21 0:15 [Bug c/115570] New: array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]' Curt.Blank at curtronics dot com
@ 2024-06-21 0:22 ` pinskia at gcc dot gnu.org
2024-06-21 0:23 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-21 0:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115570
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|UNCONFIRMED |RESOLVED
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The warning is correct.
sizeof(long) on x86_64 is 8 rather than 4 that it was on i686.
So when you do this:
unsigned char cValue[4];
unsigned long *value = 0;
value = (unsigned long *)cValue;
*value & 0xffffffff
You get undefined behavior because you are reading 8 bytes from a 4 byte array.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/115570] array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]'
2024-06-21 0:15 [Bug c/115570] New: array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]' Curt.Blank at curtronics dot com
2024-06-21 0:22 ` [Bug middle-end/115570] " pinskia at gcc dot gnu.org
@ 2024-06-21 0:23 ` pinskia at gcc dot gnu.org
2024-06-21 0:25 ` pinskia at gcc dot gnu.org
2024-06-21 0:31 ` Curt.Blank at curtronics dot com
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-21 0:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115570
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note this code also violates C/C++ aliasing rules but that is a different
issue.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/115570] array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]'
2024-06-21 0:15 [Bug c/115570] New: array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]' Curt.Blank at curtronics dot com
2024-06-21 0:22 ` [Bug middle-end/115570] " pinskia at gcc dot gnu.org
2024-06-21 0:23 ` pinskia at gcc dot gnu.org
@ 2024-06-21 0:25 ` pinskia at gcc dot gnu.org
2024-06-21 0:31 ` Curt.Blank at curtronics dot com
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-21 0:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115570
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note there is also an alignment requirement that you violate with the
assignment and access of the char array too.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/115570] array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]'
2024-06-21 0:15 [Bug c/115570] New: array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]' Curt.Blank at curtronics dot com
` (2 preceding siblings ...)
2024-06-21 0:25 ` pinskia at gcc dot gnu.org
@ 2024-06-21 0:31 ` Curt.Blank at curtronics dot com
3 siblings, 0 replies; 5+ messages in thread
From: Curt.Blank at curtronics dot com @ 2024-06-21 0:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115570
--- Comment #4 from Curtis J Blank <Curt.Blank at curtronics dot com> ---
Thank you the information.
So I should use unsigned int now on x86_64?
Where can I read more on the rule violations and what would be the proper so do
this?
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-06-21 0:31 UTC | newest]
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2024-06-21 0:15 [Bug c/115570] New: array subscript 'long unsigned int[0]' is partly outside array bounds of 'unsigned char[4]' Curt.Blank at curtronics dot com
2024-06-21 0:22 ` [Bug middle-end/115570] " pinskia at gcc dot gnu.org
2024-06-21 0:23 ` pinskia at gcc dot gnu.org
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