gcc (GCC) 4.6.0 20100415 (experimental) -O2 -g ----------------------------------------------------------------------------- void __attribute__((noinline)) f (int l) { char s[l]; } int main (void) { f (5); return 0; } ----------------------------------------------------------------------------- <2><63>: Abbrev Number: 5 (DW_TAG_variable) <64> DW_AT_name : s <68> DW_AT_type : <0x74> <1><74>: Abbrev Number: 7 (DW_TAG_array_type) <2><7d>: Abbrev Number: 8 (DW_TAG_subrange_type) <82> DW_AT_upper_bound : <0x59> <2><59>: Abbrev Number: 4 (DW_TAG_variable) <5a> DW_AT_artificial : 1 <5b> DW_AT_type : <0x8a> <5f> DW_AT_location : 0x83 (location list) <1><8a>: Abbrev Number: 10 (DW_TAG_const_type) <8b> DW_AT_type : <0x87> <1><87>: Abbrev Number: 9 (DW_TAG_base_type) <88> DW_AT_byte_size : 8 <89> DW_AT_encoding : 7 (unsigned)
<2><4c>: Abbrev Number: 3 (DW_TAG_formal_parameter) <4d> DW_AT_name : l <51> DW_AT_type : <0x6d> <55> DW_AT_location : 0x60 (location list) <1><6d>: Abbrev Number: 6 (DW_TAG_base_type) <6e> DW_AT_byte_size : 4 <6f> DW_AT_encoding : 5 (signed) <70> DW_AT_name : int Contents of the .debug_loc section: Offset Begin End Expression 00000060 0000000000400460 0000000000400468 (DW_OP_reg5) 00000060 <End of list> 00000083 0000000000400460 0000000000400463 (DW_OP_breg5: 0; DW_OP_const1u: 32; DW_OP_shl; DW_OP_const1u: 32; DW_OP_shra; DW_OP_const1s: -1; DW_OP_plus) 00000083 0000000000400463 0000000000400468 (DW_OP_breg5: -1) 00000083 0000000000400468 000000000040046c (DW_OP_breg5: -31) 00000083 <End of list> ----------------------------------------------------------------------------- I believe the loclist at 0x83 should have DW_OP_stack_value on each line. Even according to recent (offlist) mail by Jakub these are "location expressions". I do not see in the DWARF spec. an explicit description what should mean a DIE reference for DW_AT_upper_bound, currently generated by GCC as: <82> DW_AT_upper_bound : <0x59> I believe it was designed to supply there the real variable "l" holding the value such as if it would be: <82> DW_AT_upper_bound : <0x4c> If an artificial variable calculating the same value is used the artificial variable should simulate it has such _value_ (and not such its _address_). (This problem is also affecting Fortran dynamic arrays with -O2 -g.) -- Summary: VLA artificial length var loclist is missing DW_OP_stack_value Product: gcc Version: 4.6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: debug AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: jan dot kratochvil at redhat dot com GCC target triplet: x86_64-unknown-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43762