Previously we only have an extension that warn void pointer deferencing
in C++, but for C we did nothing.
C2x 6.5.3.2p4 says The unary * operator denotes indirection. If it points
to an object, the result is an lvalue designating the object. However, there
is no way to form an lvalue designating an object of an incomplete type as
6.3.2.1p1 says "an lvalue is an expression (with an object type other than
void)", so the behavior is undefined.
Fixes https://github.com/llvm/llvm-project/issues/53631
Signed-off-by: Jun Zhang <jun@junz.org>
Differential Revision: https://reviews.llvm.org/D134461
Clang has traditionally allowed C programs to implicitly convert
integers to pointers and pointers to integers, despite it not being
valid to do so except under special circumstances (like converting the
integer 0, which is the null pointer constant, to a pointer). In C89,
this would result in undefined behavior per 3.3.4, and in C99 this rule
was strengthened to be a constraint violation instead. Constraint
violations are most often handled as an error.
This patch changes the warning to default to an error in all C modes
(it is already an error in C++). This gives us better security posture
by calling out potential programmer mistakes in code but still allows
users who need this behavior to use -Wno-error=int-conversion to retain
the warning behavior, or -Wno-int-conversion to silence the diagnostic
entirely.
Differential Revision: https://reviews.llvm.org/D129881
A significant number of our tests in C accidentally use functions
without prototypes. This patch converts the function signatures to have
a prototype for the situations where the test is not specific to K&R C
declarations. e.g.,
void func();
becomes
void func(void);
This is the second batch of tests being updated (there are a significant
number of other tests left to be updated).
Compiling the following causes clang to crash
```
char *cmp(__attribute__((address_space(1))) char *x, __attribute__((address_space(2))) char *y) {
return x < y ? x : y;
}
```
with the message: "wrong cast for pointers in different address
spaces(must be an address space cast)!"
This is because during IR emission, the source and dest type for a
bitcast should not have differing address spaces.
This fix prints an error since the code shouldn't compile in the first place.
Differential Revision: https://reviews.llvm.org/D50278
llvm-svn: 339167
"bottom-up" when implicit casts and comparisons are inserted, compute them
"top-down" when the full expression is finished. Makes it easier to
coordinate warnings and thus implement -Wconversion for signedness
conversions without double-warning with -Wsign-compare. Also makes it possible
to realize that a signedness conversion is okay because the context is
performing the inverse conversion. Also simplifies some logic that was
trying to calculate the ultimate comparison/result type and getting it wrong.
Also fixes a problem with the C++ explicit casts which are often "implemented"
in the AST with a series of implicit cast expressions.
llvm-svn: 103174
destination type for initialization, assignment, parameter-passing,
etc. The main issue fixed here is that we used rather confusing
wording for diagnostics such as
t.c:2:9: warning: initializing 'char const [2]' discards qualifiers,
expected 'char *' [-pedantic]
char *name = __func__;
^ ~~~~~~~~
We're not initializing a 'char const [2]', we're initializing a 'char
*' with an expression of type 'char const [2]'. Similar problems
existed for other diagnostics in this area, so I've normalized them all
with more precise descriptive text to say what we're
initializing/converting/assigning/etc. from and to. The warning for
the code above is now:
t.c:2:9: warning: initializing 'char *' from an expression of type
'char const [2]' discards qualifiers [-pedantic]
char *name = __func__;
^ ~~~~~~~~
Fixes <rdar://problem/7447179>.
llvm-svn: 100832
- This is designed to make it obvious that %clang_cc1 is a "test variable"
which is substituted. It is '%clang_cc1' instead of '%clang -cc1' because it
can be useful to redefine what gets run as 'clang -cc1' (for example, to set
a default target).
llvm-svn: 91446
DiagnoseSignCompare into Sema::CheckSignCompare and call it from more places.
Add some enumerator tests. These seem to expose some oddities in the
types we're converting C++ enumerators to; in particular, they're converting
to unsigned before int, which seems to contradict 4.5 [conv.prom] p2.
Note to self: stop baiting Doug in my commit messages.
llvm-svn: 86128
Remove diagnostics from Sema::CheckIndirectionOperand(). C89/C99 allow dereferencing an incomplete type. clang appears to be emulating some incorrect gcc behavior (see below).
void
foo (void)
{
struct b;
struct b* x = 0;
struct b* y = &*x; // gcc produces an error ("dereferencing pointer to incomplete type")
}
With this patch, the above is now allowed.
Bug/Patch by Eli Friedman!
llvm-svn: 45933
Jun Zhang