Thanks to changes to type compatibility rules via WG14 N3007, these
functions can now be called with a compatible type even within the same
TU, which makes the -Wvisibility diagnostic too chatty to have on by
default.
So in C23 mode, -Wvisibility will only diagnose an incomplete tag type
declared in a function prototype. If the tag is defined in the
prototype, the diagnostic is silenced.
This changes the type compatibility rules so that it is permitted to
redefine tag types within the same TU so long as they are equivalent
definitions.
It is intentionally not being exposed as an extension in older C
language modes. GCC does not do so and the feature doesn't seem
compelling enough to warrant it.
Unlike C++, C allows the definition of an uninitialized `const` object.
If the object has static or thread storage duration, it is still
zero-initialized, otherwise, the object is left uninitialized. In either
case, the code is not compatible with C++.
This adds a new diagnostic group, `-Wdefault-const-init-unsafe`, which
is on by default and diagnoses any definition of a `const` object which
remains uninitialized.
It also adds another new diagnostic group, `-Wdefault-const-init` (which
also enabled the `unsafe` variant) that diagnoses any definition of a
`const` object (including ones which are zero-initialized). This
diagnostic is off by default.
Finally, it adds `-Wdefault-const-init` to `-Wc++-compat`. GCC diagnoses
these situations under this flag.
Fixes#19297
A file scope declaration without an initializer which is neither extern
nor thread_local is a tentative definition. If the declaration of an
identifier for an object is a tentative definition and has internal
linkage, the declared type shall not be an incomplete type.
Clang was previously failing to diagnose this in -pedantic mode.
Fixes#50661
---------
Co-authored-by: Mariya Podchishchaeva <mariya.podchishchaeva@intel.com>
C99 introduced macros of the form `INTn_C(v)` which expand to a signed
or unsigned integer constant with the specified value `v` and the type
`int_leastN_t`. Clang's initial implementation of these macros used
token pasting to form the integer constants, but this means that users
cannot define a macro named `L`, `U`, `UL`, etc before including
`<stdint.h>` (in freestanding mode, where Clang's header is being used)
because that could form invalid token pasting results. The new
definitions now use the predefined `__INTn_C` macros instead of using
token pasting. This matches the behavior of GCC.
Fixes#85995
Reverts llvm/llvm-project#94159
@zygoloid had some concerns about the implementation of this, which make
sense to me, so I’d like to revert this for now so we can have more time
to think about how to best approach this (if at all...)
This adds a fix-it hint in situations where a modifiable lvalue is expected, but a prvalue
or non-modifiable lvalue of pointer type was found, so long as dereferencing the pointer
would result in a modifiable lvalue.
Resolves#93066
This is now allowed in C23; continue to diagnose it in earlier language
modes as before, but now as a C23 extension rather than a GNU extension.
This fixes#83658.
GNU and MSVC have extensions where flexible array members (or their
equivalent) can be in unions or alone in structs. This is already fully
supported in Clang through the 0-sized array ("fake flexible array")
extension or when C99 flexible array members have been syntactically
obfuscated.
Clang needs to explicitly allow these extensions directly for C99
flexible arrays, since they are common code patterns in active use by
the
Linux kernel (and other projects). Such projects have been using either
0-sized arrays (which is considered deprecated in favor of C99 flexible
array members) or via obfuscated syntax, both of which complicate their
code bases.
For example, these do not error by default:
```
union one {
int a;
int b[0];
};
union two {
int a;
struct {
struct { } __empty;
int b[];
};
};
```
But this does:
```
union three {
int a;
int b[];
};
```
Remove the default error diagnostics for this but continue to provide
warnings under Microsoft or GNU extensions checks. This will allow for
a seamless transition for code bases away from 0-sized arrays without
losing existing code patterns. Add explicit checking for the warnings
under various constructions.
Additionally fixes a CodeGen bug with flexible array members in unions
in C++, which was found when adding a testcase for:
```
union { char x[]; } z = {0};
```
which only had Sema tests originally.
Fixes#84565
Our existing diagnostics for catching unsequenced modifications handles
test coverage for N1282, which is correcting the standard based on the
resolution of DR087.
Add functionality to APInt::toString() that allows it to insert
separators between groups of digits, using the C++ literal
separator ' between groups.
Fixes issue #58228
Reviewers: @AaronBallman, @cjdb, @tbaederr
This follows the same implementation logic as with C++ and is
compatible with the GCC behavior in C.
Trigraphs are enabled by default in -std=c* conformance modes before
C23, but are disabled in GNU and Microsoft modes as well as in C23 or
later.
Fixes https://github.com/llvm/llvm-project/issues/58637.
Adds `isAlignas()` method on `AttributeCommonInfo` which accounts for
C++ `alignas` as well as C11 `_Alignas`.
The method is used to improve diagnostic in C when `_Alignas` is used in
C at the wrong location. This corrects the previously suggested move
of `_Alignas` past the declaration specifier, now warns attribute
`_Alignas` is ignored.
Based on https://reviews.llvm.org/D141177.
These are an artifact of how types are structured but serve little
purpose, merely showing that the type is sugared in some way. For
example, ElaboratedType's existence means struct S gets printed as
'struct S':'struct S' in the AST, which is unnecessary visual clutter.
Note that skipping the second print when the types have the same string
matches what we do for diagnostics, where the aka will be skipped.
C2x was finalized at the June 2023 WG14 meeting. The DIS is out for
balloting and the comment period for that closes later this year/early
next year. While that does leave an opportunity for more changes to the
standard during the DIS ballot resolution process, only editorial
changes are anticipated and as a result, the C committee considers C2x
to be final. The committee took a straw poll on what we'd prefer the
informal name of the standard be, and we decided it should be called
C23 regardless of what year ISO publishes it.
However, because the final publication is not out, this patch does not
add the language standard alias for the -std=iso9899:<year> spelling of
the standard mode; that will be added once ISO finally publishes the
document and the year chosen will match the publication date.
This also changes the value of __STDC_VERSION__ from the placeholder
value 202000L to the final value 202311L.
Subsequent patches will start renaming things from c2x to c23, cleaning
up documentation, etc.
Differential Revision: https://reviews.llvm.org/D157606
This reverts commit dfdfd306cfaf54fbc43e2d5eb36489dac3eb9976.
An issue is reported for wrong warning, this has to be reconsidered.
Differential Revision: https://reviews.llvm.org/D157352
This fix PR37919
The below code produces -Wconstant-logical-operand for the first statement,
but not the second.
void foo(int x) {
if (x && 5) {}
if (5 && x) {}
}
Reviewed By: nickdesaulniers
Differential Revision: https://reviews.llvm.org/D142609
This fixes running tests with a toolchain that defaults to a MinGW
target.
After the previous attempt with this patch, this is now changed to
use !defined(__MINGW32__) instead of defined(_MSC_VER) to distinguish
between MSVC and MinGW mode; Clang doesn't define _MSC_VER when invoked
with "clang -cc1" as some of those tests do.
Differential Revision: https://reviews.llvm.org/D149997
This was a mistake from e7300e75b51a7e7d4e81975b4be7a6c65f9a8286
(https://reviews.llvm.org/D133574) caused by us accidentally tracking
an older copy of the C DR list for DR496. The text in
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2396.htm#dr_496 makes
it clear that subobjects are allowed, which means member and array
access expressions are allowed.
This backs out the changes from the previous commit that relate to this
diagnostic.
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm made very
clear that it is an UB having type definitions with in offsetof.
Clang supports defining a type as the first argument as a conforming
extension due to how many projects use the construct in C99 and earlier
to calculate the alignment of a type. GCC also supports defining a type
as the first argument.
This adds extension warnings and documentation for the functionality
Clang explicitly supports.
Fixes#57065
Reverts the revert of 39da55e8f548a11f7dadefa73ea73d809a5f1729
Co-authored-by: Yingchi Long <i@lyc.dev>
Co-authored-by: Aaron Ballman <aaron@aaronballman.com>
Differential Revision: https://reviews.llvm.org/D133574
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm made very
clear that it is an UB having type definitions with in offsetof.
Clang supports defining a type as the first argument as a conforming
extension due to how many projects use the construct in C99 and earlier
to calculate the alignment of a type. GCC also supports defining a type
as the first argument.
This adds extension warnings and documentation for the functionality
Clang explicitly supports.
Fixes#57065
Co-authored-by: Yingchi Long <i@lyc.dev>
Co-authored-by: Aaron Ballman <aaron@aaronballman.com>
In general, the source tree is not assumed to be writeable, so modifying `%s` does not work for all CI systems. Instead of touching `%s`, copy it to a writeable dir using `%t`, and touch it there.
Actually, `dr0xx.c` isn't really needed at all, so just create a new `dep.c` file in the build tree.
This was recently added in cb088e8c3abf30456e2891f90b5194d0070c387a, fixed in 1481fcf780bde7b115aa395064d71749b1a40889, and fixed again in d16c59013056f1bf8844ded8faeb0cf01b1c3613.
If dr0xx.c's timestamp is newer than dr324.c the preprocessor will issue
an unexpected diagnostic in dr324.c. To prevent this diagnostic we can
have dr324.c run touch against itself to force its timestamp to be new.
The test uses
#pragma GCC dependency "oops\..\dr0xx.c"
to test preprocessor "tokenization obscurities". However, that
pragma also emits a warning if the refered file is newer than the
current file -- and d694e2490af8 edited dr0xx.c, causing this warning
to fire.
As workaround, touch this file, so that it's newer than dr0xx.c again.
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
We would diagnose use of `long long` as an extension in C89 and C++98
modes when the user spelled the type `long long` or used the `LL`
literal suffix, but failed to diagnose when the literal had no suffix
but required a `long long` to represent the value.
