[llvm-bugs] [Bug 25934] New: Incorrect debug info generated for variable size arrays

via llvm-bugs llvm-bugs at lists.llvm.org
Wed Dec 23 05:49:25 PST 2015


            Bug ID: 25934
           Summary: Incorrect debug info generated for variable size
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: tberghammer at google.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Reproducing the issue:
* Compile the followoing code snippet with "clang++ -g var.cpp":
int main() {
    for (int i = 0; i < 10; ++i) {
        int x[i + 1];
* Inspect the debug info for variable 'x'

The relevant parts of the debug info:
 <4><6b>: Abbrev Number: 5 (DW_TAG_variable)
    <6c>   DW_AT_location    : 0x0      (location list)
    <70>   DW_AT_name        : (indirect string, offset: 0x71): x       
    <74>   DW_AT_decl_file   : 1        
    <75>   DW_AT_decl_line   : 3        
    <76>   DW_AT_type        : <0x84>

<1><84>: Abbrev Number: 7 (DW_TAG_array_type)
    <85>   DW_AT_type        : <0x7d>   
 <2><89>: Abbrev Number: 8 (DW_TAG_subrange_type)
    <8a>   DW_AT_type        : <0x8f>   
 <2><8e>: Abbrev Number: 0
 <1><8f>: Abbrev Number: 9 (DW_TAG_base_type)
    <90>   DW_AT_name        : (indirect string, offset: 0x73): sizetype        
    <94>   DW_AT_byte_size   : 8        
    <95>   DW_AT_encoding    : 7        (unsigned)
 <1><96>: Abbrev Number: 0

The problem is that clang specifies a DW_TAG_subrange_type under
DW_TAG_array_type but is fails to fill it in with some information specifying
the number of elements in the array (DW_AT_count or DW_AT_upper_bound).

The issue is reproduced with clang 3.5.0 and with 3.8.0 (trunk 256170). Gcc
4.8.4 generates correct debug info with producing a DW_AT_upper_bound
containing a dwarf expression to a memory location containing the current array

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