| Message ID | 507ED72D.7080403@oracle.com |
|---|---|
| State | New |
| Headers | show |
Hmm, I thought I fixed a very similar bug recently. I'm concerned that this change will cause problems with brace-elision situations. But then again, can we have a zero-length array followed by anything else? Jason
Hi, On 10/18/2012 03:17 AM, Jason Merrill wrote: > Hmm, I thought I fixed a very similar bug recently. > > I'm concerned that this change will cause problems with brace-elision > situations. But then again, can we have a zero-length array followed > by anything else? If I understand correctly your hesitations, I don't think there are exceptions to the general rule that if the size of the array is zero there can be no initializers. This morning I investigated in some detail this special case (from a testcase I recently added, pr43765.C): struct SomeType { const char *values[]; }; it's in fact related because we parse it as: struct SomeType { const char *values[0]; }; (per grokdeclarator around line 10246). Given the way we parse it (not completely uncontroversial, IMHO, but that would be a separate issue), we do the right thing, we accept: SomeType s = { }; and we reject: SomeType s = { 1 }; Only the wording of the error changes (from "too many initializers" to "initializers provided") (*) In any case, I can't imagine a different, safer, way to handle the issue we are facing. Do you have anything specific to suggest? Thanks, Paolo. (*) Moreover we likewise accept: SomeType s = { { } }; and likewise reject: SomeType s = { { { } } };
On 10/18/2012 01:15 AM, Paolo Carlini wrote: > If I understand correctly your hesitations, I don't think there are > exceptions to the general rule that if the size of the array is zero > there can be no initializers. I'm thinking of a testcase like this, which is currently accepted: struct A { int i[0]; int j; }; struct A a = { 1 }; Here, since i has no elements, we should skip over it and apply the one initializer to j. Jason
On 10/18/2012 06:02 PM, Jason Merrill wrote: > On 10/18/2012 01:15 AM, Paolo Carlini wrote: >> If I understand correctly your hesitations, I don't think there are >> exceptions to the general rule that if the size of the array is zero >> there can be no initializers. > > I'm thinking of a testcase like this, which is currently accepted: > > struct A > { > int i[0]; > int j; > }; > > struct A a = { 1 }; > > Here, since i has no elements, we should skip over it and apply the > one initializer to j. Ah, Ok, I was missing the "skipping" thing ;) Let me see how we can handle this... it seems tricky. Paolo.
Index: cp/decl.c =================================================================== --- cp/decl.c (revision 192527) +++ cp/decl.c (working copy) @@ -5022,10 +5022,6 @@ reshape_init_array_1 (tree elt_type, tree max_inde if (sized_array_p) { - /* Minus 1 is used for zero sized arrays. */ - if (integer_all_onesp (max_index)) - return new_init; - if (host_integerp (max_index, 1)) max_index_cst = tree_low_cst (max_index, 1); /* sizetype is sign extended, not zero extended. */ @@ -5068,6 +5064,14 @@ reshape_init_array (tree type, reshape_iter *d, ts if (TYPE_DOMAIN (type)) max_index = array_type_nelts (type); + /* Minus 1 is used for zero sized arrays. */ + if (max_index && integer_all_onesp (max_index)) + { + if (complain & tf_error) + error ("initializers provided for zero-size array of type %qT", type); + return error_mark_node; + } + return reshape_init_array_1 (TREE_TYPE (type), max_index, d, complain); } Index: testsuite/g++.dg/parse/pr43765.C =================================================================== --- testsuite/g++.dg/parse/pr43765.C (revision 192527) +++ testsuite/g++.dg/parse/pr43765.C (working copy) @@ -11,4 +11,4 @@ SomeType vals[] = { { values : temp, }, 0 - }; // { dg-error "invalid" } + }; // { dg-error "zero-size" } Index: testsuite/g++.dg/init/array30.C =================================================================== --- testsuite/g++.dg/init/array30.C (revision 0) +++ testsuite/g++.dg/init/array30.C (working copy) @@ -0,0 +1,7 @@ +// PR c++/54501 +// { dg-options "" } + +int main() +{ + int a[][0] = {0}; // { dg-error "zero-size" } +} Index: testsuite/g++.dg/init/array0.C =================================================================== --- testsuite/g++.dg/init/array0.C (revision 192527) +++ testsuite/g++.dg/init/array0.C (working copy) @@ -8,5 +8,5 @@ void foo() unsigned char dir; int data[0]; } yanito; - static const yanito horse = { 1, { 2, 3 } }; // { dg-error "too many" } + static const yanito horse = { 1, { 2, 3 } }; // { dg-error "zero-size" } }