erichkeane created this revision.
erichkeane added reviewers: aaron.ballman, spatel, RKSimon.
As identified and briefly discussed here:
https://bugs.llvm.org/show_bug.cgi?id=37305
Converting a floating point number to an integer type when
the integral part is out of the range of the integer type is
undefined behavior in C. Additionally, CodeGen emits an undef
in this situation.
HOWEVER, we've been giving a warning that says that the value is
changed. This patch corrects the warning to list that it is actually
undefined behavior.
Repository:
rC Clang
https://reviews.llvm.org/D46535
Files:
include/clang/Basic/DiagnosticSemaKinds.td
lib/Sema/SemaChecking.cpp
test/SemaCXX/coroutines.cpp
test/SemaCXX/warn-float-conversion.cpp
test/SemaCXX/warn-literal-conversion.cpp
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -9429,6 +9429,20 @@
unsigned DiagID = 0;
if (IsLiteral) {
+ // Conversion of a floating point value to a non-bool integer where the
+ // integral part cannot be represented by the integer type is undefined.
+ if (!IsBool) {
+ if (IntegerValue.isSigned() &&
+ (IntegerValue.isMaxSignedValue() || IntegerValue.isMinSignedValue()))
+ return DiagnoseImpCast(
+ S, E, T, CContext,
+ diag::warn_impcast_literal_float_to_integer_out_of_range);
+ if (IntegerValue.isUnsigned() &&
+ (IntegerValue.isMaxValue() || IntegerValue.isMinValue()))
+ return DiagnoseImpCast(
+ S, E, T, CContext,
+ diag::warn_impcast_literal_float_to_integer_out_of_range);
+ }
// Warn on floating point literal to integer.
DiagID = diag::warn_impcast_literal_float_to_integer;
} else if (IntegerValue == 0) {
@@ -9444,12 +9458,19 @@
return DiagnoseImpCast(S, E, T, CContext,
diag::warn_impcast_float_integer, PruneWarnings);
}
+ if (!IsBool && (IntegerValue.isMaxValue() || IntegerValue.isMinValue()))
+ return DiagnoseImpCast(S, E, T, CContext,
+ diag::warn_impcast_float_to_integer_out_of_range,
+ PruneWarnings);
} else { // IntegerValue.isSigned()
if (!IntegerValue.isMaxSignedValue() &&
!IntegerValue.isMinSignedValue()) {
return DiagnoseImpCast(S, E, T, CContext,
diag::warn_impcast_float_integer, PruneWarnings);
}
+ return DiagnoseImpCast(S, E, T, CContext,
+ diag::warn_impcast_float_to_integer_out_of_range,
+ PruneWarnings);
}
// Warn on evaluatable floating point expression to integer conversion.
DiagID = diag::warn_impcast_float_to_integer;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -3140,14 +3140,20 @@
def warn_impcast_literal_float_to_integer : Warning<
"implicit conversion from %0 to %1 changes value from %2 to %3">,
InGroup<LiteralConversion>;
+def warn_impcast_literal_float_to_integer_out_of_range : Warning<
+ "implicit conversion of out of range value from %0 to %1 is undefined">,
+ InGroup<LiteralConversion>;
def warn_impcast_float_integer : Warning<
"implicit conversion turns floating-point number into integer: %0 to %1">,
InGroup<FloatConversion>, DefaultIgnore;
def warn_impcast_float_to_integer : Warning<
"implicit conversion of out of range value from %0 to %1 changes value "
"from %2 to %3">,
InGroup<FloatOverflowConversion>, DefaultIgnore;
+def warn_impcast_float_to_integer_out_of_range : Warning<
+ "implicit conversion of out of range value from %0 to %1 is undefined">,
+ InGroup<FloatOverflowConversion>, DefaultIgnore;
def warn_impcast_float_to_integer_zero : Warning<
"implicit conversion from %0 to %1 changes non-zero value from %2 to %3">,
InGroup<FloatZeroConversion>, DefaultIgnore;
Index: test/SemaCXX/coroutines.cpp
===================================================================
--- test/SemaCXX/coroutines.cpp
+++ test/SemaCXX/coroutines.cpp
@@ -157,7 +157,7 @@
void yield() {
co_yield 0;
co_yield {"foo", 1, 2};
- co_yield {1e100}; // expected-error {{cannot be narrowed}} expected-note {{explicit cast}} expected-warning {{changes value}} expected-warning {{braces around scalar}}
+ co_yield {1e100}; // expected-error {{cannot be narrowed}} expected-note {{explicit cast}} expected-warning {{implicit conversion}} expected-warning {{braces around scalar}}
co_yield {"foo", __LONG_LONG_MAX__}; // expected-error {{cannot be narrowed}} expected-note {{explicit cast}} expected-warning {{changes value}}
co_yield {"foo"};
co_yield "foo"; // expected-error {{no matching}}
Index: test/SemaCXX/warn-literal-conversion.cpp
===================================================================
--- test/SemaCXX/warn-literal-conversion.cpp
+++ test/SemaCXX/warn-literal-conversion.cpp
@@ -48,4 +48,11 @@
// values.
bool b3 = 0.0f;
bool b4 = 0.0;
+
+ // These all warn because they overflow the target type.
+ short s = 32768.0; // expected-warning{{implicit conversion of out of range value from 'double' to 'short' is undefined}}
+ unsigned short us = 65536.0; // expected-warning{{implicit conversion of out of range value from 'double' to 'unsigned short' is undefined}}
+
+ short s2 = -32769.0; // expected-warning{{implicit conversion of out of range value from 'double' to 'short' is undefined}}
+ unsigned short us2 = -65537.0; // expected-warning{{implicit conversion of out of range value from 'double' to 'unsigned short' is undefined}}
}
Index: test/SemaCXX/warn-float-conversion.cpp
===================================================================
--- test/SemaCXX/warn-float-conversion.cpp
+++ test/SemaCXX/warn-float-conversion.cpp
@@ -81,9 +81,9 @@
char b = -500.0; // caught by -Wliteral-conversion
const float LargeNumber = 1024;
- char c = LargeNumber; // expected-warning{{implicit conversion of out of range value from 'const float' to 'char' changes value from 1024 to 127}}
- char d = 400.0 + 400.0; // expected-warning{{implicit conversion of out of range value from 'double' to 'char' changes value from 800 to 127}}
+ char c = LargeNumber; // expected-warning{{implicit conversion of out of range value from 'const float' to 'char' is undefined}}
+ char d = 400.0 + 400.0; // expected-warning{{implicit conversion of out of range value from 'double' to 'char' is undefined}}
- char e = 1.0 / 0.0; // expected-warning{{implicit conversion of out of range value from 'double' to 'char' changes value from +Inf to 127}}
+ char e = 1.0 / 0.0; // expected-warning{{implicit conversion of out of range value from 'double' to 'char' is undefined}}
}
#endif // OVERFLOW
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