C++ PATCH to detect narrowing in case values (PR c++/90805)
Marek Polacek
polacek@redhat.com
Thu Jun 13 21:03:00 GMT 2019
Case values are converted constant expressions, so narrowing conversion is not
permitted. This patch adds detecting narrowing to case_conversion; it's a
handy spot because we have both the value and the (adjusted) type of the
condition.
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2019-06-13 Marek Polacek <polacek@redhat.com>
PR c++/90805 - detect narrowing in case values.
* decl.c (case_conversion): Detect narrowing in case values.
* c-c++-common/pr89888.c: Update expected dg-error.
* g++.dg/cpp0x/Wnarrowing17.C: New test.
diff --git gcc/cp/decl.c gcc/cp/decl.c
index 0a3ef452536..655de1ea6af 100644
--- gcc/cp/decl.c
+++ gcc/cp/decl.c
@@ -3610,16 +3610,21 @@ case_conversion (tree type, tree value)
value = mark_rvalue_use (value);
+ if (INTEGRAL_OR_UNSCOPED_ENUMERATION_TYPE_P (type))
+ type = type_promotes_to (type);
+
if (cxx_dialect >= cxx11
&& (SCOPED_ENUM_P (type)
|| !INTEGRAL_OR_UNSCOPED_ENUMERATION_TYPE_P (TREE_TYPE (value))))
- {
- if (INTEGRAL_OR_UNSCOPED_ENUMERATION_TYPE_P (type))
- type = type_promotes_to (type);
- value = (perform_implicit_conversion_flags
- (type, value, tf_warning_or_error,
- LOOKUP_IMPLICIT | LOOKUP_NO_NON_INTEGRAL));
- }
+ value = (perform_implicit_conversion_flags
+ (type, value, tf_warning_or_error,
+ LOOKUP_IMPLICIT | LOOKUP_NO_NON_INTEGRAL));
+
+ /* The constant-expression VALUE shall be a converted constant expression
+ of the adjusted type of the switch condition, which doesn't allow
+ narrowing conversions. */
+ check_narrowing (type, value, tf_warning_or_error, /*const_only=*/true);
+
return cxx_constant_value (value);
}
diff --git gcc/testsuite/c-c++-common/pr89888.c gcc/testsuite/c-c++-common/pr89888.c
index d9e11d6f26a..f14881ca052 100644
--- gcc/testsuite/c-c++-common/pr89888.c
+++ gcc/testsuite/c-c++-common/pr89888.c
@@ -11,8 +11,8 @@ foo (unsigned char x)
{
case -1: y = -1; break; /* { dg-message "previously used here" } */
/* { dg-warning "case label value is less than minimum value for type" "" { target *-*-* } .-1 } */
- case 0xffffffff: y = 0xffffffff; break; /* { dg-error "duplicate case value" } */
- case ~0U: y = ~0U; break; /* { dg-error "duplicate case value" } */
+ case 0xffffffff: y = 0xffffffff; break; /* { dg-error "duplicate case value|narrowing" } */
+ case ~0U: y = ~0U; break; /* { dg-error "duplicate case value|narrowing" } */
}
}
diff --git gcc/testsuite/g++.dg/cpp0x/Wnarrowing17.C gcc/testsuite/g++.dg/cpp0x/Wnarrowing17.C
new file mode 100644
index 00000000000..064de531cb3
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp0x/Wnarrowing17.C
@@ -0,0 +1,19 @@
+// PR c++/90805 - detect narrowing in case values.
+// { dg-do compile { target c++11 } }
+
+void f(int i, char c, unsigned u)
+{
+ switch (i)
+ {
+ case 2149056512u:; // { dg-error "narrowing conversion of .2149056512. from .unsigned int. to .int." }
+ case (long long int) 1e10:; // { dg-error "narrowing conversion of .10000000000. from .long long int. to .int." }
+ // { dg-warning "overflow in conversion" "overflow" { target *-*-* } .-1 }
+ }
+
+ switch (c)
+ // No narrowing, the adjusted type is int.
+ case 300:; // { dg-warning "exceeds maximum value for type" }
+
+ switch (u)
+ case -42:; // { dg-error "narrowing conversion of .-42. from .int. to .unsigned int." }
+}
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