https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98780
Bug ID: 98780
Summary: Missing line table entry for inlined stmt at -g -O0
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
Created attachment 50018
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50018&action=edit
source file
[ Spinoff of gdb PR25884 - "Stepping over inlined function without line number
statement fails" (https://sourceware.org/bugzilla/show_bug.cgi?id=25884). ]
Consider test source gdb/testsuite/gdb.opt/inline-cmds.c (attached).
When compiled with -O0 -g, this bit:
...
71 result = 0; /* set breakpoint 3 here */
72
73 func1 (); /* first call */
74 func1 (); /* second call */
75 marker ();
...
where func1 is:
...
33 inline __attribute__((always_inline)) int func1(void)
34 {
35 bar ();
36 return x * y;
37 }
...
is represented in the line info as:
...
Line number Starting address View Stmt
71 0x64 x
35 0x6e x
75 0x78 x
...
where the insn are:
...
64: c7 05 00 00 00 00 00 movl $0x0,0x0(%rip) # 6e <main+0x6e>
6b: 00 00 00
6e: e8 00 00 00 00 callq 73 <bar>
73: e8 00 00 00 00 callq 78 <bar>
78: e8 00 00 00 00 callq 7d <marker>
...
The calls to bar at 6e and 73 represent different instantiations of the same
statement, but they get a single entry in the line table.
It would be more accurate to have two entries.
Note that each call to bar has its own DW_TAG_inlined_subroutine descriptor:
...
<2><11e>: Abbrev Number: 10 (DW_TAG_inlined_subroutine)
<11f> DW_AT_abstract_origin: <0x208>
<123> DW_AT_low_pc : 0x6e
<12b> DW_AT_high_pc : 0x5
<133> DW_AT_call_file : 1
<134> DW_AT_call_line : 73
<135> DW_AT_call_column : 3
<2><136>: Abbrev Number: 10 (DW_TAG_inlined_subroutine)
<137> DW_AT_abstract_origin: <0x208>
<13b> DW_AT_low_pc : 0x73
<143> DW_AT_high_pc : 0x5
<14b> DW_AT_call_file : 1
<14c> DW_AT_call_line : 74
<14d> DW_AT_call_column : 3
...
so at some level gcc knows that these are different statements.
[ The problem with gdb is that it ignores the DW_TAG_inlined_subroutine on the
second call because there's no corresponding line table entry. ]
