[Bug c/23106] New: -Wstrict-aliasing=2 doesn't warn for all aliasing problems
Hi,
This program:
int main() {
int a = 1;
* (short *) (char *) &a = 2;
char *p = (char *) &a;
* (short *) p = 3;
return a;
}
returns 1 when compiled with gcc 4.0.1 (nothing more is necessary than gcc -O2
test.c). However, adding -Wstrict-aliasing=2 does not make any warning for this
show up. This happens with void * as well.
I first asked about the first case on gcc-help, and Ian Lance Taylor followed up
with a patch to show a warning:
http://gcc.gnu.org/ml/gcc-help/2005-07/msg00292.html
For the second case, he asked to open a bug here.
--
Summary: -Wstrict-aliasing=2 doesn't warn for all aliasing
problems
Product: gcc
Version: 4.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: fn_x at hotmail dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23106
[Bug c/23106] -Wstrict-aliasing=2 doesn't warn for all aliasing problems
--- Additional Comments From fn_x at hotmail dot com 2005-07-28 00:00 --- The bug this is marked a duplicate of is about -Wall, which includes only -Wstrict-aliasing. This bug is about -Wstrict-aliasing=2. It is documented as warning for "all code which might break the strict aliasing rules that the compiler is using for optimization". I certainly agree that it is reasonable not to warn when only -Wstrict-aliasing is given, but if you don't want to warn here either, would it be fair to ask to at least update the documentation? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23106
[Bug c/23106] -Wstrict-aliasing=2 doesn't warn for all aliasing problems
--- Additional Comments From fn_x at hotmail dot com 2005-07-28 05:26 --- Consider this reopened as a documentation bug, then, as it is currently clearly documented that the second case will get a warning with -Wstrict-aliasing=2. -- What|Removed |Added Status|RESOLVED|UNCONFIRMED Resolution|DUPLICATE | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23106
[Bug c++/23385] New: gcc accepts "class typedefname" when typedefname is defined in a nested class and references a template parameter
Hello,
All versions of gcc I tried (2.95.3, 3.3.6, 3.4.4, 4.0-20050811, and
4.1-20050813) accept this code without any warnings or errors (using -ansi
-pedantic -Wall -W, just in case)
template
class A {
struct helper { typedef T type; };
friend class helper::type;
};
class B { A m; } b;
int main() {}
I don't believe this code is valid. icc 9.0.021 rejects this code with
error: typedef "type" may not be used in an elaborated type specifier
and gcc 4.0-20050811 rejects it when I try the same thing with A::type,
rather than A::helper::type, with
error: using template type parameter T after class
Additionally, any attempts at using "class A::helper::type" outside of the
template definition result in
error: using typedef-name A::helper::type after class
So I think my code should result in either of the above two errors as well.
I can't find any other reports of this, but sorry if I missed anything.
--
Summary: gcc accepts "class typedefname" when typedefname is
defined in a nested class and references a template
parameter
Product: gcc
Version: 4.0.2
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: fn_x at hotmail dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23385
[Bug c++/23385] gcc accepts "class typedefname" when typedefname is defined in a nested class and references a template parameter
--- Additional Comments From fn_x at hotmail dot com 2005-08-14 16:48 --- Yeah, this is just slightly different code, but it is covered by that bug's summary and description. Sorry for the noise. *** This bug has been marked as a duplicate of 21498 *** -- What|Removed |Added Status|UNCONFIRMED |RESOLVED Resolution||DUPLICATE http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23385
[Bug c++/21498] clause 7.1.5.3/2 of the c++ is not enforced
--- Additional Comments From fn_x at hotmail dot com 2005-08-14 16:48 --- *** Bug 23385 has been marked as a duplicate of this bug. *** -- What|Removed |Added CC||fn_x at hotmail dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21498
[Bug c/26494] New: -pedantic-errors can be overridden by -W*
This simple incorrect program:
int main() { puts("Hello"); }
when compiled with gcc -std=c99 -pedantic-errors is rejected with
test.c: In function main:
test.c:1: error: implicit declaration of function puts
However, add -Wall to the options, and it becomes:
test.c: In function main:
test.c:1: warning: implicit declaration of function puts
and the program compiles and runs without errors. I think gcc should not
compile it. Also, reordering the options doesn't change anything.
Given how old this is (I can see it with gcc 3.3.6, 3.4.5, 4.0.2 and
4.1(20060223)), I'm a bit surprised if it hasn't come up before, but I searched
bugzilla and didn't find anything. Sorry for anything I missed.
--
Summary: -pedantic-errors can be overridden by -W*
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: fn_x at hotmail dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26494
[Bug c/18493] New: gcc doesn't like switch blocks without case/default labels
Hi,
int main() {
goto bug;
switch(0) {
bug: return 0;
}
}
This program doesn't compile with gcc 3.4.3. It gives this error message:
/tmp/ccetXBGt.o(.text+0x1d): In function `main':
: undefined reference to `.L2'
However, this:
int main() {
goto bug;
switch(0) {
bug: return 0;
default: ;
}
}
does compile without a problem.
gcc 2.95.3 and 3.3.4 compile both examples.
I searched to see if anyone else reported this, and only found bug #17078. I
don't know if it's related or just similar. Sorry if I overlooked another bug
report.
--
Summary: gcc doesn't like switch blocks without case/default
labels
Product: gcc
Version: 3.4.3
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: fn_x at hotmail dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18493
