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Fix Wbitfield-constant-conversion false positives 

Summary:
The diagnostic did not handle ~ well. An expression such as ~0 is often used when 'all ones' is needed.

Differential Revision: https://reviews.llvm.org/D24232

llvm-svn: 282156
This commit is contained in:
Daniel Marjamaki 2016-09-22 14:13:46 +00:00
parent ba1598975f
commit ee5b5f52ba
2 changed files with 11 additions and 6 deletions
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7
clang/lib/Sema/SemaChecking.cpp
View File

@ -8006,11 +8006,10 @@ bool AnalyzeBitFieldAssignment(Sema &S, FieldDecl *Bitfield, Expr *Init,
unsigned OriginalWidth = Value.getBitWidth();
unsigned FieldWidth = Bitfield->getBitWidthValue(S.Context);
if (Value.isSigned() && Value.isNegative())
if (!Value.isSigned() || Value.isNegative())
if (UnaryOperator *UO = dyn_cast<UnaryOperator>(OriginalInit))
if (UO->getOpcode() == UO_Minus)
if (isa<IntegerLiteral>(UO->getSubExpr()))
OriginalWidth = Value.getMinSignedBits();
if (UO->getOpcode() == UO_Minus || UO->getOpcode() == UO_Not)
OriginalWidth = Value.getMinSignedBits();
if (OriginalWidth <= FieldWidth)
return false;

10
clang/test/Sema/constant-conversion.c
View File

@ -69,7 +69,8 @@ void test7() {
unsigned int reserved:28;
} f;
f.twoBits1 = ~1; // expected-warning {{implicit truncation from 'int' to bitfield changes value from -2 to 2}}
f.twoBits1 = ~0; // no-warning
f.twoBits1 = ~1; // no-warning
f.twoBits2 = ~2; // expected-warning {{implicit truncation from 'int' to bitfield changes value from -3 to 1}}
f.twoBits1 &= ~1; // no-warning
f.twoBits2 &= ~2; // no-warning
@ -114,6 +115,8 @@ void test9() {
char array_init[] = { 255, 127, 128, 129, 0 };
}
#define A 1
void test10() {
struct S {
unsigned a : 4;
@ -121,7 +124,10 @@ void test10() {
s.a = -1;
s.a = 15;
s.a = -8;
s.a = ~0;
s.a = ~0U;
s.a = ~(1<<A);
s.a = -9; // expected-warning{{implicit truncation from 'int' to bitfield changes value from -9 to 7}}
s.a = -9; // expected-warning{{implicit truncation from 'int' to bitfield changes value from -9 to 7}}
s.a = 16; // expected-warning{{implicit truncation from 'int' to bitfield changes value from 16 to 0}}
}