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* [Bug c/63643] New: pointer to const variable doesn't allow to change its value (on Mac OS)
@ 2014-10-25 11:41 romain.wallon at orange dot fr
2014-10-25 11:47 ` [Bug c/63643] " dominiq at lps dot ens.fr
2014-10-26 1:40 ` redi at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: romain.wallon at orange dot fr @ 2014-10-25 11:41 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63643
Bug ID: 63643
Summary: pointer to const variable doesn't allow to change its
value (on Mac OS)
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: romain.wallon at orange dot fr
Created attachment 33806
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33806&action=edit
A program which tests changing a const value with a pointer.
For example, when a variable i is declared as const int, and p is declared as
int *, it is impossible to change the value of i by *p, whereas ANSI norm
allows it.
More over, it seems to be two differents value at the same address. Here is the
result of a test:
0x7fff5720dbf8 : 0
0x7fff5720dbf8 : 12
You'll find the program in attachment.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/63643] pointer to const variable doesn't allow to change its value (on Mac OS)
2014-10-25 11:41 [Bug c/63643] New: pointer to const variable doesn't allow to change its value (on Mac OS) romain.wallon at orange dot fr
@ 2014-10-25 11:47 ` dominiq at lps dot ens.fr
2014-10-26 1:40 ` redi at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: dominiq at lps dot ens.fr @ 2014-10-25 11:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63643
Dominique d'Humieres <dominiq at lps dot ens.fr> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |WAITING
Last reconfirmed| |2014-10-25
Ever confirmed|0 |1
--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
On x86_64-apple-darwin14 (Yosemite) I get
0x7fff58ce0414 : 12
0x7fff58ce0414 : 12
When compiling the test with -Wall -Wextra -pedantic I get
pr63643.c: In function 'main':
pr63643.c:7:9: warning: format '%p' expects argument of type 'void *', but
argument 2 has type 'const int *' [-Wformat=]
printf("%p : %d\n", &i, i);
^
pr63643.c:7:9: warning: format '%p' expects argument of type 'void *', but
argument 2 has type 'const int *' [-Wformat=]
pr63643.c:8:9: warning: format '%p' expects argument of type 'void *', but
argument 2 has type 'int *' [-Wformat=]
printf("%p : %d\n", p, *p);
^
pr63643.c:8:9: warning: format '%p' expects argument of type 'void *', but
argument 2 has type 'int *' [-Wformat=]
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/63643] pointer to const variable doesn't allow to change its value (on Mac OS)
2014-10-25 11:41 [Bug c/63643] New: pointer to const variable doesn't allow to change its value (on Mac OS) romain.wallon at orange dot fr
2014-10-25 11:47 ` [Bug c/63643] " dominiq at lps dot ens.fr
@ 2014-10-26 1:40 ` redi at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: redi at gcc dot gnu.org @ 2014-10-26 1:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63643
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The program is invalid. The C standard says "An assignment operator shall have
a modifiable lvalue as its left operand." An object with a const-qualified type
is not a modifiable lvalue.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-10-26 1:35 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2014-10-25 11:41 [Bug c/63643] New: pointer to const variable doesn't allow to change its value (on Mac OS) romain.wallon at orange dot fr
2014-10-25 11:47 ` [Bug c/63643] " dominiq at lps dot ens.fr
2014-10-26 1:40 ` redi at gcc dot gnu.org
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