From bb73f0e6ef2adb5055a6ddc66cdcbd26dbdeb3fe Mon Sep 17 00:00:00 2001 From: David Bolvansky Date: Tue, 2 Oct 2018 06:02:30 +0000 Subject: Added warning for unary minus used with unsigned type Summary: Inspired by MSVC, which found some occurrences of this expression on our code base. Fixes PR38950 Reviewers: rsmith, craig.topper, spatel, RKSimon, aaron.ballman, thakis Reviewed By: rsmith Subscribers: joerg, Quuxplusone, lebedev.ri, craig.topper, RKSimon, cfe-commits Differential Revision: https://reviews.llvm.org/D52137 --- clang/include/clang/Basic/DiagnosticSemaKinds.td | 6 ++++++ clang/lib/Sema/SemaChecking.cpp | 13 +++++++++++++ clang/test/Sema/unary-minus-integer-impcast.c | 20 ++++++++++++++++++++ 3 files changed, 39 insertions(+) create mode 100644 clang/test/Sema/unary-minus-integer-impcast.c diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index 7a95b53a51a..85450d7f397 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -3197,6 +3197,12 @@ def warn_impcast_integer_sign_conditional : Warning< def warn_impcast_integer_precision : Warning< "implicit conversion loses integer precision: %0 to %1">, InGroup, DefaultIgnore; +def warn_impcast_high_order_zero_bits : Warning< + "higher order bits are zeroes after implicit conversion">, + InGroup, DefaultIgnore; +def warn_impcast_nonnegative_result : Warning< + "the resulting value is always non-negative after implicit conversion">, + InGroup, DefaultIgnore; def warn_impcast_integer_64_32 : Warning< "implicit conversion loses integer precision: %0 to %1">, InGroup, DefaultIgnore; diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp index a258d349c68..d6183dde95f 100644 --- a/clang/lib/Sema/SemaChecking.cpp +++ b/clang/lib/Sema/SemaChecking.cpp @@ -10896,6 +10896,19 @@ CheckImplicitConversion(Sema &S, Expr *E, QualType T, SourceLocation CC, return DiagnoseImpCast(S, E, T, CC, diag::warn_impcast_integer_precision); } + if (TargetRange.Width > SourceRange.Width) { + if (auto *UO = dyn_cast(E)) + if (UO->getOpcode() == UO_Minus) + if (Source->isUnsignedIntegerType()) { + if (Target->isUnsignedIntegerType()) + return DiagnoseImpCast(S, E, T, CC, + diag::warn_impcast_high_order_zero_bits); + if (Target->isSignedIntegerType()) + return DiagnoseImpCast(S, E, T, CC, + diag::warn_impcast_nonnegative_result); + } + } + if (TargetRange.Width == SourceRange.Width && !TargetRange.NonNegative && SourceRange.NonNegative && Source->isSignedIntegerType()) { // Warn when doing a signed to signed conversion, warn if the positive diff --git a/clang/test/Sema/unary-minus-integer-impcast.c b/clang/test/Sema/unary-minus-integer-impcast.c new file mode 100644 index 00000000000..0eb44017588 --- /dev/null +++ b/clang/test/Sema/unary-minus-integer-impcast.c @@ -0,0 +1,20 @@ +// RUN: %clang_cc1 %s -verify -Wconversion -fsyntax-only -triple x86_64-pc-linux-gnu +// RUN: %clang_cc1 %s -verify -Wconversion -fsyntax-only -triple i386-pc-linux-gnu + +void test(void) { + unsigned int a = 1; + + unsigned long long b = -a; // expected-warning {{higher order bits are zeroes after implicit conversion}} + long long c = -a; // expected-warning {{the resulting value is always non-negative after implicit conversion}} + + unsigned long b2 = -a; +#ifdef __x86_64__ +// expected-warning@-2 {{higher order bits are zeroes after implicit conversion}} +#endif + long c2 = -a; +#ifdef __x86_64__ +// expected-warning@-2 {{the resulting value is always non-negative after implicit conversion}} +#else +// expected-warning@-4 {{implicit conversion changes signedness: 'unsigned int' to 'long'}} +#endif +} -- cgit v1.2.3