https://llvm.org/bugs/show_bug.cgi?id=30620
Bug ID: 30620
Summary: clang emits code for constructors that causes
debuggers to behave unexpectedly
Product: clang
Version: unspecified
Hardware: PC
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: edmu...@microsoft.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
This is reported by jacda...@microsoft.com (he's waiting for his account on
lldvm.org/bugs to be created):
clang emits a wrapper constructor whose purpose is to invoke child
constructors, copy constructors, and ultimately, the real constructor of a
class.
This wrapper constructor is mapped to the same source code as the real
constructor and is not marked with a trampoline symbol (which would tell the
debugger to continue stepping through that code) or the target no-stmt flag in
the line info.
Unfortunately, this means that both gdb and lldb (when debugging this clang
compiled binary) stop in the wrapper constructor rather than the targets. Now,
when a bp is set in the source of the real constructor, the debugger will stop
when that bp is hit. The logical callstack (not displayed in the window) then
looks like this:
real_ctor
wrapper_ctor
main
Stepping off the end of the real constructor stops in the wrapper constructor.
Interesting symbols:
wrapper constructor disassem
a.out`CSquid::CSquid:
0x100000f60 <+0>: pushq %rbp
0x100000f61 <+1>: movq %rsp, %rbp
0x100000f64 <+4>: subq $0x10, %rsp
0x100000f68 <+8>: movq %rdi, -0x8(%rbp)
0x100000f6c <+12>: movq -0x8(%rbp), %rdi
0x100000f70 <+16>: callq 0x100000fa0 ; call to real
constructor CSquid::CSquid at constructorbug.cpp:8
0x100000f79 <+25>: popq %rbp
0x100000f7a <+26>: retq
0x100000f7b <+27>: nopl (%rax,%rax)
real constructor disassem:
.out`CSquid::CSquid:
0x100000fa0 <+0>: pushq %rbp
0x100000fa1 <+1>: movq %rsp, %rbp
0x100000fa4 <+4>: movq %rdi, -0x8(%rbp)
0x100000fa8 <+8>: movq -0x8(%rbp), %rdi
0x100000fb2 <+18>: popq %rbp
0x100000fb3 <+19>: req
Wrapper constructor subprogram symbol:
0x000000b8: TAG_subprogram [11] *
AT_low_pc( 0x0000000100000f60 )
AT_high_pc( 0x0000000100000f7b )
AT_frame_base( rbp )
AT_object_pointer( {0x000000db} )
AT_MIPS_linkage_name( "_ZN6CSquidC1Ev" )
AT_specification( {0x0000000000000044}"CSquid" )
0x000000db: TAG_formal_parameter [12]
AT_location( fbreg -8 )
AT_name( "this" )
AT_type( {0x0000000000000165} ( CSquid* ) )
AT_artificial( 0x01 )
0x000000ec: NULL
Real constructor subprogram symbol:
0x00000130: TAG_subprogram [11] *
AT_low_pc( 0x0000000100000fa0 )
AT_high_pc( 0x0000000100000fb4 )
AT_frame_base( rbp )
AT_object_pointer( {0x00000153} )
AT_MIPS_linkage_name( "_ZN6CSquidC2Ev" )
AT_specification( {0x0000000000000044}"CSquid" )
0x00000153: TAG_formal_parameter [12]
AT_location( fbreg -8 )
AT_name( "this" )
AT_type( {0x0000000000000165} ( CSquid* ) )
AT_artificial( 0x01 )
0x00000164: NULL
Line table for both:
0x0000004f: DW_LNE_set_address( 0x0000000100000f60 )
0x0000005a: address += 0, line += 7
0x0000000100000f60 1 8 0 is_stmt
0x0000005b: DW_LNS_set_column( 5 )
0x0000005d: DW_LNS_set_prologue_end
0x0000005e: address += 10, line += 0
0x0000000100000f70 1 8 5 is_stmt prologue_end
0x0000005f: address += 5, line += 2
0x0000000100000f75 1 10 5 is_stmt
0x00000060: DW_LNS_advance_pc( 6 )
0x00000062: DW_LNE_end_sequence
0x0000000100000f7b 1 10 5 is_stmt
0x00000082: DW_LNE_set_address( 0x0000000100000fa0 )
0x0000008d: address += 0, line += 7
0x0000000100000fa0 1 8 0 is_stmt
0x0000008e: DW_LNS_set_column( 13 )
0x00000090: DW_LNS_set_prologue_end
0x00000091: address += c, line += 1
0x0000000100000fac 1 9 13 is_stmt prologue_end
0x00000092: DW_LNS_set_column( 5 )
0x00000094: address += 6, line += 1
0x0000000100000fb2 1 10 5 is_stmt
0x00000095: DW_LNS_advance_pc( 2 )
0x00000097: DW_LNE_end_sequence
0x0000000100000fb4 1 10 5 is_stmt
--
You are receiving this mail because:
You are on the CC list for the bug.
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
