`[[clang::fallthrough]]` has meaning for the CFG, but all other
StmtAttrs we currently have don't. So omit them, as AttributedStatements
with children cause several issues and there's no benefit in including
them.
Fixes PR52103 and PR49454. See PR52103 for details.
Differential Revision: https://reviews.llvm.org/D111568
The Linux kernel has a macro called IS_ENABLED(), which evaluates to a
constant 1 or 0 based on Kconfig selections, allowing C code to be
unconditionally enabled or disabled at build time. For example:
int foo(struct *a, int b) {
switch (b) {
case 1:
if (a->flag || !IS_ENABLED(CONFIG_64BIT))
return 1;
__attribute__((fallthrough));
case 2:
return 2;
default:
return 3;
}
}
There is an unreachable warning about the fallthrough annotation in the
first case because !IS_ENABLED(CONFIG_64BIT) can be evaluated to 1,
which looks like
return 1;
__attribute__((fallthrough));
to clang.
This type of warning is pointless for the Linux kernel because it does
this trick all over the place due to the sheer number of configuration
options that it has.
Add -Wunreachable-code-fallthrough, enabled under -Wunreachable-code, so
that projects that want to warn on unreachable code get this warning but
projects that do not care about unreachable code can still use
-Wimplicit-fallthrough without having to make changes to their code
base.
Fixes PR51094.
Reviewed By: aaron.ballman, nickdesaulniers
Differential Revision: https://reviews.llvm.org/D107933
Set the source ranges for parsed GNU-style attributes in
ParseGNUAttributes(), the same way that ParseCXX11Attributes() does it.
Differential Revision: https://reviews.llvm.org/D75844
Set the source ranges for parsed GNU-style attributes in
ParseGNUAttributes(), the same way that ParseCXX11Attributes() does it.
Differential Revision: https://reviews.llvm.org/D75844
Clang currently automates a fair amount of diagnostic checking for
declaration attributes based on the declarations in Attr.td. It checks
for things like subject appertainment, number of arguments, language
options, etc. This patch uses the same machinery to perform diagnostic
checking on statement attributes.
This matches a similar behavior with GCC accepting [[gnu::__attr__]] as a alias for [[gnu::attr]] in that clang attributes can now be spelled with two leading and trailing underscores.
I had always intended for this to work, but missed the critical bit. We already had an existing test in test/Preprocessor/has_attribute.cpp for [[clang::__fallthrough__]] but using that spelling would still give an "unknown attribute" diagnostic.
llvm-svn: 346547
exactly the same as clang's existing [[clang::fallthrough]] attribute, which
has been updated to have the same semantics. The one significant difference
is that [[fallthrough]] is ill-formed if it's not used immediately before a
switch label (even when -Wimplicit-fallthrough is disabled). To support that,
we now build a CFG of any function that uses a '[[fallthrough]];' statement
to check.
In passing, fix some bugs with our support for statement attributes -- in
particular, diagnose their use on declarations, rather than asserting.
llvm-svn: 262881
Summary:
-Wimplicit-fallthrough: fixed two cases where "fallthrough annotation in unreachable code" was issued incorrectly:
1. In actual unreachable code, but not immediately on a fall-through execution
path "fallthrough annotation does not directly precede switch label" is better;
2. After default: in a switch with covered enum cases. Actually, these shouldn't
be treated as unreachable code for our purpose.
Reviewers: rsmith
Reviewed By: rsmith
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D374
llvm-svn: 174575
cases in switch statements. Also add a [[clang::fallthrough]] attribute, which
can be used to suppress the warning in the case of intentional fallthrough.
Patch by Alexander Kornienko!
The handling of C++11 attribute namespaces in this patch is temporary, and will
be replaced with a cleaner mechanism in a subsequent patch.
llvm-svn: 156086
Nico Weber