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Enable support for the [[fallthrough]] attribute from WG14 N2052 when enabling double square bracket attributes in C code.

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llvm-svn: 316083
This commit is contained in:
Aaron Ballman
2017-10-18 14:33:27 +00:00
parent 9723f12491
commit 8c6b1a3bf2
3 changed files with 83 additions and 9 deletions
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2
clang/include/clang/Basic/Attr.td
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@@ -1009,7 +1009,7 @@ def ExtVectorType : Attr {
}
def FallThrough : StmtAttr {
let Spellings = [CXX11<"", "fallthrough", 201603>,
let Spellings = [CXX11<"", "fallthrough", 201603>, C2x<"", "fallthrough">,
CXX11<"clang", "fallthrough">];
// let Subjects = [NullStmt];
let Documentation = [FallthroughDocs];

15
clang/lib/Sema/AnalysisBasedWarnings.cpp
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@@ -1291,16 +1291,15 @@ static StringRef getFallthroughAttrSpelling(Preprocessor &PP,
static void DiagnoseSwitchLabelsFallthrough(Sema &S, AnalysisDeclContext &AC,
bool PerFunction) {
// Only perform this analysis when using C++11. There is no good workflow
// for this warning when not using C++11. There is no good way to silence
// the warning (no attribute is available) unless we are using C++11's support
// for generalized attributes. Once could use pragmas to silence the warning,
// but as a general solution that is gross and not in the spirit of this
// warning.
// Only perform this analysis when using [[]] attributes. There is no good
// workflow for this warning when not using C++11. There is no good way to
// silence the warning (no attribute is available) unless we are using
// [[]] attributes. One could use pragmas to silence the warning, but as a
// general solution that is gross and not in the spirit of this warning.
//
// NOTE: This an intermediate solution. There are on-going discussions on
// NOTE: This an intermediate solution. There are on-going discussions on
// how to properly support this warning outside of C++11 with an annotation.
if (!AC.getASTContext().getLangOpts().CPlusPlus11)
if (!AC.getASTContext().getLangOpts().DoubleSquareBracketAttributes)
return;
FallthroughMapper FM(S);

75
clang/test/Sema/c2x-fallthrough.c Normal file
View File

@@ -0,0 +1,75 @@
// RUN: %clang_cc1 -fsyntax-only -fdouble-square-bracket-attributes -verify %s
void f(int n) {
switch (n) {
case 0:
n += 1;
[[fallthrough]]; // ok
case 1:
if (n) {
[[fallthrough]]; // ok
} else {
return;
}
case 2:
for (int n = 0; n != 10; ++n)
[[fallthrough]]; // expected-error {{does not directly precede switch label}}
case 3:
while (1)
[[fallthrough]]; // expected-error {{does not directly precede switch label}}
case 4:
while (0)
[[fallthrough]]; // expected-error {{does not directly precede switch label}}
case 5:
do [[fallthrough]]; while (1); // expected-error {{does not directly precede switch label}}
case 6:
do [[fallthrough]]; while (0); // expected-error {{does not directly precede switch label}}
case 7:
switch (n) {
case 0:
// FIXME: This should be an error, even though the next thing we do is to
// fall through in an outer switch statement.
[[fallthrough]];
}
case 8:
[[fallthrough]]; // expected-error {{does not directly precede switch label}}
goto label;
label:
case 9:
n += 1;
case 10: // no warning, -Wimplicit-fallthrough is not enabled in this test, and does not need to
// be enabled for these diagnostics to be produced.
break;
}
}
[[fallthrough]] typedef int n; // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
typedef int [[fallthrough]] n; // expected-error {{'fallthrough' attribute cannot be applied to types}}
typedef int n [[fallthrough]]; // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
enum [[fallthrough]] E { // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
One
};
struct [[fallthrough]] S { // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
int i;
};
[[fallthrough]] // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
void g(void) {
[[fallthrough]] int n; // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
[[fallthrough]] ++n; // expected-error-re {{{{^}}fallthrough attribute is only allowed on empty statements}}
switch (n) {
// FIXME: This should be an error.
[[fallthrough]];
return;
case 0:
[[fallthrough, fallthrough]]; // expected-error {{multiple times}}
case 1:
[[fallthrough(0)]]; // expected-error {{argument list}}
case 2:
break;
}
}