https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87059
--- Comment #8 from Aldy Hernandez <aldyh at redhat dot com> --- On 08/23/2018 04:08 PM, msebor at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87059 > > --- Comment #7 from Martin Sebor <msebor at gcc dot gnu.org> --- > The MIN_EXPR code predates my change -- r255898 just moved indentation. Based > on past experience I would assume MIN_EXPR to need the same types. The code > in > expand_builtin_strncmp mixes ssizetype and sizetype: > > len1 = c_strlen (arg1, 1); // returns ssizetype > len2 = c_strlen (arg2, 1); > > if (len1) > len1 = size_binop_loc (loc, PLUS_EXPR, ssize_int (1), len1); > if (len2) > len2 = size_binop_loc (loc, PLUS_EXPR, ssize_int (1), len2); > > len3 = fold_convert_loc (loc, sizetype, arg3); > ... > if (len != len3) > len = fold_build2_loc (loc, MIN_EXPR, TREE_TYPE (len), len, len3); > > So the fix is presumably to change len3 to > > len3 = fold_convert_loc (loc, ssizetype, arg3); > > Given the difference between sizetype and ssizetype is just one 's' it seems > like an easy mistake to make. If MIN_EXPR does, in fact, require arguments of > the same type then adding an assertion to fold_binary_loc() to verify it would > help expose these mistakes early. I'm not sure what the right predicate is to > use in the assertion. Just compare TYPE_MAIN_VARIANT of the two argument > types > for equality? > Thanks. Testing the following: gcc/ PR 87059/tree-optimization * builtins.c (expand_builtin_strncmp): Pass signed sizetype to fold_convert_loc. diff --git a/gcc/builtins.c b/gcc/builtins.c index b1a79f3f33f..7113d19aadf 100644 --- a/gcc/builtins.c +++ b/gcc/builtins.c @@ -4727,7 +4727,7 @@ expand_builtin_strncmp (tree exp, ATTRIBUTE_UNUSED rtx target, if (len2) len2 = size_binop_loc (loc, PLUS_EXPR, ssize_int (1), len2); - tree len3 = fold_convert_loc (loc, sizetype, arg3); + tree len3 = fold_convert_loc (loc, ssizetype, arg3); /* If we don't have a constant length for the first, use the length of the second, if we know it. If neither string is constant length,
