diff options
Diffstat (limited to 'gcc/c-common.c')
| -rw-r--r-- | gcc/c-common.c | 35 |
1 files changed, 30 insertions, 5 deletions
diff --git a/gcc/c-common.c b/gcc/c-common.c index edc9b2c..6872e3a 100644 --- a/gcc/c-common.c +++ b/gcc/c-common.c @@ -1280,6 +1280,14 @@ conversion_warning (tree type, tree expr) else if (TREE_CODE (TREE_TYPE (expr)) == INTEGER_TYPE && TREE_CODE (type) == INTEGER_TYPE) { + /* Don't warn about unsigned char y = 0xff, x = (int) y; */ + int uns; + tree orig_expr = expr; + expr = get_narrower (expr, &uns); + + if (expr == orig_expr) + uns = TYPE_UNSIGNED (TREE_TYPE (expr)); + /* Warn for integer types converted to smaller integer types. */ if (formal_prec < TYPE_PRECISION (TREE_TYPE (expr))) give_warning = true; @@ -1287,14 +1295,31 @@ conversion_warning (tree type, tree expr) /* When they are the same width but different signedness, then the value may change. */ else if ((formal_prec == TYPE_PRECISION (TREE_TYPE (expr)) - && TYPE_UNSIGNED (TREE_TYPE (expr)) != TYPE_UNSIGNED (type)) + && uns != TYPE_UNSIGNED (type)) /* Even when converted to a bigger type, if the type is unsigned but expr is signed, then negative values will be changed. */ - || (TYPE_UNSIGNED (type) && !TYPE_UNSIGNED (TREE_TYPE (expr)))) - warning (OPT_Wsign_conversion, - "conversion to %qT from %qT may change the sign of the result", - type, TREE_TYPE (expr)); + || (TYPE_UNSIGNED (type) && !uns)) + { + if (uns != TYPE_UNSIGNED (TREE_TYPE (expr))) + { + /* For signed char s1, s2 = (int) (unsigned char) s1; + get_narrower returns s1, but uns = 1. Find the + narrowest type with uns == TYPE_UNSIGNED (type). */ + tree unsexpr = orig_expr; + + while (TREE_CODE (unsexpr) == NOP_EXPR + && unsexpr != expr + && TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (unsexpr, + 0))) + == uns) + unsexpr = TREE_OPERAND (unsexpr, 0); + expr = unsexpr; + } + warning (OPT_Wsign_conversion, + "conversion to %qT from %qT may change the sign of the result", + type, TREE_TYPE (expr)); + } } /* Warn for integer types converted to real types if and only if |