[Bug middle-end/33086] warn for read-only uninitialized variables passed as arguments

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33086

Martin Sebor  changed:

   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 CC||msebor at gcc dot gnu.org
 Resolution|--- |DUPLICATE

--- Comment #6 from Martin Sebor  ---
I think it would be reasonable to issue a warning on the code in comment #3
(perhaps under -Wmaybe-uninitialized rather than -Wuninitialized).  For
uninitialized variables passed by reference to pure functions (that cannot
change objects pointed to by their arguments) I think it would make sense to
issue -Wunitialized.

Based on comment #4 and on my understanding of the two reports resolving as a
duplicate of bug 10138.

*** This bug has been marked as a duplicate of bug 10138 ***

[Bug middle-end/33086] warn for read-only uninitialized variables passed as arguments

[manu at gcc dot gnu dot org]

--- Comment #5 from manu at gcc dot gnu dot org  2007-08-20 14:47 ---
Andrew, what about functions marked with attribute "pure" ?

int atoi(const char *) __attribute__ ((pure));


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33086

[Bug middle-end/33086] warn for read-only uninitialized variables passed as arguments

[manu at gcc dot gnu dot org]

--- Comment #4 from manu at gcc dot gnu dot org  2007-08-17 10:15 ---
(In reply to comment #3)
> 
> void use(const int *a)
> {
>   int *b = (int*)a;

Andrew, you are right. I tend to forget how fragile is 'const', even in C++.
So, then this is invalid and thus it is PR10138.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33086

[Bug middle-end/33086] warn for read-only uninitialized variables passed as arguments

[pinskia at gcc dot gnu dot org]

--- Comment #3 from pinskia at gcc dot gnu dot org  2007-08-16 14:58 ---


void use(const int *a)
{
  int *b = (int*)a;
b[0] = 5;
}
void foo(void)
{
  int i;
  use(&i);
}


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33086

[Bug middle-end/33086] warn for read-only uninitialized variables passed as arguments

[manu at gcc dot gnu dot org]

--- Comment #2 from manu at gcc dot gnu dot org  2007-08-16 11:19 ---
(In reply to comment #1)
> > At least for languages where 'const' is actually enforced
> 
> There is none, 

void use(const int *a)
{
a[0] = 5;
}
void foo(void)
{
  int i;
  use(&i);
}

new.c:3: error: assignment of read-only location

Either I am misunderstanding you or your argument about overwriting the pointer
argument is equivalent to just don't using the value of 'i'. Of course, we
don't know whether the value is used or not within use() but the fact is that
'i' cannot be initialized within use().


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manu at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||manu at gcc dot gnu dot org
   Priority|P5  |P3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33086

[Bug middle-end/33086] warn for read-only uninitialized variables passed as arguments

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||pinskia at gcc dot gnu dot
   ||org
   Priority|P3  |P5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33086

[Bug middle-end/33086] warn for read-only uninitialized variables passed as arguments

[pinskia at gcc dot gnu dot org]

--- Comment #1 from pinskia at gcc dot gnu dot org  2007-08-16 10:59 ---
> At least for languages where 'const' is actually enforced

There is none, unless you are taking about fortran "in" arguments.  So we need
to mark such argument as special.

Now if you have the full program (or at least the containts of use function),
and you can prove it never writes to the incoming pointer argument, then you
can warn but only then.

In C and C++ you can never tell without the body of use.


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pinskia at gcc dot gnu dot org changed:

   What|Removed |Added

OtherBugsDependingO|24639   |
  nThis||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33086