C89 had a questionable feature where the compiler would implicitly
declare a function that the user called but was never previously
declared. The resulting function would be globally declared as
extern int func(); -- a function without a prototype which accepts zero
or more arguments.
C99 removed support for this questionable feature due to severe
security concerns. However, there was no deprecation period; C89 had
the feature, C99 didn't. So Clang (and GCC) both supported the
functionality as an extension in C99 and later modes.
C2x no longer supports that function signature as it now requires all
functions to have a prototype, and given the known security issues with
the feature, continuing to support it as an extension is not tenable.
This patch changes the diagnostic behavior for the
-Wimplicit-function-declaration warning group depending on the language
mode in effect. We continue to warn by default in C89 mode (due to the
feature being dangerous to use). However, because this feature will not
be supported in C2x mode, we've diagnosed it as being invalid for so
long, the security concerns with the feature, and the trivial
workaround for users (declare the function), we now default the
extension warning to an error in C99-C17 mode. This still gives users
an easy workaround if they are extensively using the extension in those
modes (they can disable the warning or use -Wno-error to downgrade the
error), but the new diagnostic makes it more clear that this feature is
not supported and should be avoided. In C2x mode, we no longer allow an
implicit function to be defined and treat the situation the same as any
other lookup failure.
Differential Revision: https://reviews.llvm.org/D122983
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 first batch of tests being updated (there are a significant
number of other tests left to be updated).
The dependency mechanism for C has been implemented, and we have rolled out
this to all internal users, didn't see crashy issues, we consider it is stable
enough.
Differential Revision: https://reviews.llvm.org/D89046
While here, wordsmith the error a bit. Now clang says:
error: filter expression has non-integral type 'Foo'
Fixes PR43779
Reviewers: amccarth
Differential Revision: https://reviews.llvm.org/D69969
Since continue, break, return are much more common than __finally, this tries
to keep the work for continue, break, return O(1). Sema keeps a stack of active
__finally scopes (to do this, ActOnSEHFinally() is split into
ActOnStartSEHFinally() and ActOnFinishSEHFinally()), and the various jump
statements then check if the current __finally scope (if present) is deeper
than then destination scope of the jump.
The same warning for goto statements is still missing.
This is the moral equivalent of MSVC's C4532.
llvm-svn: 231623
Previously we would simply double-emit the body of the __finally block,
but that doesn't work when it contains any kind of Decl, which we can't
double emit.
This fixes that by emitting the block once and branching into a shared
code region and then branching back out.
llvm-svn: 228222
The lowering looks a lot like normal EH lowering, with the exception
that the exceptions are caught by executing filter expression code
instead of matching typeinfo globals. The filter expressions are
outlined into functions which are used in landingpad clauses where
typeinfo would normally go.
Major aspects that still need work:
- Non-call exceptions in __try bodies won't work yet. The plan is to
outline the __try block in the frontend to keep things simple.
- Filter expressions cannot use local variables until capturing is
implemented.
- __finally blocks will not run after exceptions. Fixing this requires
work in the LLVM SEH preparation pass.
The IR lowering looks like this:
// C code:
bool safe_div(int n, int d, int *r) {
__try {
*r = normal_div(n, d);
} __except(_exception_code() == EXCEPTION_INT_DIVIDE_BY_ZERO) {
return false;
}
return true;
}
; LLVM IR:
define i32 @filter(i8* %e, i8* %fp) {
%ehptrs = bitcast i8* %e to i32**
%ehrec = load i32** %ehptrs
%code = load i32* %ehrec
%matches = icmp eq i32 %code, i32 u0xC0000094
%matches.i32 = zext i1 %matches to i32
ret i32 %matches.i32
}
define i1 zeroext @safe_div(i32 %n, i32 %d, i32* %r) {
%rr = invoke i32 @normal_div(i32 %n, i32 %d)
to label %normal unwind to label %lpad
normal:
store i32 %rr, i32* %r
ret i1 1
lpad:
%ehvals = landingpad {i8*, i32} personality i32 (...)* @__C_specific_handler
catch i8* bitcast (i32 (i8*, i8*)* @filter to i8*)
%ehptr = extractvalue {i8*, i32} %ehvals, i32 0
%sel = extractvalue {i8*, i32} %ehvals, i32 1
%filter_sel = call i32 @llvm.eh.seh.typeid.for(i8* bitcast (i32 (i8*, i8*)* @filter to i8*))
%matches = icmp eq i32 %sel, %filter_sel
br i1 %matches, label %eh.except, label %eh.resume
eh.except:
ret i1 false
eh.resume:
resume
}
Reviewers: rjmccall, rsmith, majnemer
Differential Revision: http://reviews.llvm.org/D5607
llvm-svn: 226760
Give scope a SEHTryScope bit, set that in ParseSEHTry(), and let Sema
walk the scope chain to find the SEHTry parent on __leave statements.
(They are rare enough that it seems better to do the walk instead of
giving Scope a SEHTryParent pointer -- this is similar to AtCatchScope.)
llvm-svn: 212422
Aaron Ballman