From: kamlesh kumar <kamleshbhalui@gmail.com>
To: gdb@sourceware.org
Subject: gdb unable to print alias variable
Date: Thu, 24 Jun 2021 06:04:19 +0530 [thread overview]
Message-ID: <CABKRkghV7rE9zfm+6phqzM6RYegu5kY5qKhJWD6d1DwTES_Dbg@mail.gmail.com> (raw)
Hi Devs,
Currently clang does not produce debug info for alias variables, I am
working on this feature, by having DW_TAG_imported_declaration for
alias variable but gdb does not work with this.
below is demonstration
consider this testcase,
-----------
int oldname = 1;
extern int newname attribute((alias("oldname")));
int main(){}
---------------------
$clang test.c -g
$gdb a.out
(gdb) pt oldname
type = int
(gdb) pt newname
type = <data variable, no debug info>
(gdb) p newname
'newname' has unknown type; cast it to its declared type
Here is debug info in ./a.out by clang
dumped debug info (using llvm-dwarfdump)
test.o: file format elf64-x86-64
.debug_info contents:
0x00000000: Compile Unit: length = 0x00000067, format = DWARF32,
version = 0x0004, abbr_offset = 0x0000, addr_size = 0x08 (next unit at
0x0000006b)
0x0000000b: DW_TAG_compile_unit
DW_AT_producer ("clang version 13.0.0
(git@github.com:llvm/llvm-project.git
4cd7169f5517167ef456e82c6dcae669bde6c725)")
DW_AT_language (DW_LANG_C99)
DW_AT_name ("test.c")
DW_AT_stmt_list (0x00000000)
DW_AT_comp_dir ("/folk/kkumar/tcllvm/llvm-build-lldb-rel/bin")
DW_AT_low_pc (0x0000000000000000)
DW_AT_high_pc (0x0000000000000008)
0x0000002a: DW_TAG_variable
DW_AT_name ("oldname")
DW_AT_type (0x0000003f "int")
DW_AT_external (true)
DW_AT_decl_file
("/folk/kkumar/tcllvm/llvm-build-lldb-rel/bin/test.c")
DW_AT_decl_line (1)
DW_AT_location (DW_OP_addr 0x0)
0x0000003f: DW_TAG_base_type
DW_AT_name ("int")
DW_AT_encoding (DW_ATE_signed)
DW_AT_byte_size (0x04)
0x00000046: DW_TAG_imported_declaration
DW_AT_decl_file
("/folk/kkumar/tcllvm/llvm-build-lldb-rel/bin/test.c")
DW_AT_decl_line (2)
DW_AT_import (0x0000002a)
DW_AT_name ("newname")
0x00000051: DW_TAG_subprogram
DW_AT_low_pc (0x0000000000000000)
DW_AT_high_pc (0x0000000000000008)
DW_AT_frame_base (DW_OP_reg6 RBP)
DW_AT_name ("main")
DW_AT_decl_file
("/folk/kkumar/tcllvm/llvm-build-lldb-rel/bin/test.c")
DW_AT_decl_line (3)
DW_AT_type (0x0000003f "int")
DW_AT_external (true)
0x0000006a: NULL
Even though the newname has desired info, gdb is unable to print the
value or type of the newname.
I would like to know whether this is a bug in gdb, or debug info
itself is wrong(because of DW_TAG_imported_declaration for newname)?
Any other viable path to address alias variable debugging will be appreciated.
./kamlesh
next reply other threads:[~2021-06-24 0:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-24 0:34 kamlesh kumar [this message]
2021-06-26 2:50 ` Simon Marchi
2021-06-27 1:49 ` David Blaikie
2021-06-27 3:10 ` kamlesh kumar
2021-06-27 16:11 ` David Blaikie
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