PR symtab/16264 - support DW_AT_main_subprogram
This patch adds support for DW_AT_main_subprogram. This is PR symtab/16264. DW_AT_main_subprogram is used to mark a program's entry point. GCC can emit this, and I hope to change the Rust compiler to emit it as well. GDB already supports an older, pre-DWARF 4 convention adopted by FORTRAN compilers, namely to emit DW_AT_calling_convention for the "main" function. However, I think this support in GDB had a small bug, in that it seems to rely on the DW_AT_name being read before DW_AT_calling_convention. This patch fixes this as well. Built and regtested on x86-64 Fedora 24 and the buildbot. New test case included. 2016-12-02 Tom Tromey <tom@tromey.com> PR symtab/16264: * dwarf2read.c (struct partial_die_info) <main_subprogram>: New member. (add_partial_symbol): Call set_objfile_main_name. (read_partial_die): Handle DW_AT_main_subprogram. <DW_AT_calling_convention>: don't call set_objfile_main_name, but set main_subprogram flag. 2016-12-02 Tom Tromey <tom@tromey.com> * gdb.dwarf2/main-subprogram.c: New file. * gdb.dwarf2/main-subprogram.exp: New file.
This commit is contained in:
Tom Tromey
parent
f5ac6ab387
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0c1b455e29
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@ -1,3 +1,13 @@
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2016-12-02 Tom Tromey <tom@tromey.com>
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PR symtab/16264:
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* dwarf2read.c (struct partial_die_info) <main_subprogram>: New
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member.
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(add_partial_symbol): Call set_objfile_main_name.
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(read_partial_die): Handle DW_AT_main_subprogram.
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<DW_AT_calling_convention>: don't call set_objfile_main_name, but
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set main_subprogram flag.
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2016-12-02 Simon Marchi <simon.marchi@ericsson.com>
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* tracefile-tfile.c (tfile_write_status): Adjust to renames.
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@ -1105,6 +1105,9 @@ struct partial_die_info
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unsigned int has_pc_info : 1;
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unsigned int may_be_inlined : 1;
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/* This DIE has been marked DW_AT_main_subprogram. */
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unsigned int main_subprogram : 1;
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/* Flag set if the SCOPE field of this structure has been
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computed. */
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unsigned int scope_set : 1;
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@ -6930,6 +6933,9 @@ add_partial_symbol (struct partial_die_info *pdi, struct dwarf2_cu *cu)
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&objfile->static_psymbols,
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addr, cu->language, objfile);
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}
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if (pdi->main_subprogram && actual_name != NULL)
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set_objfile_main_name (objfile, actual_name, cu->language);
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break;
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case DW_TAG_constant:
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{
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@ -15949,19 +15955,18 @@ read_partial_die (const struct die_reader_specs *reader,
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to describe functions' calling conventions.
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However, because it's a necessary piece of information in
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Fortran, and because DW_CC_program is the only piece of debugging
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information whose definition refers to a 'main program' at all,
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several compilers have begun marking Fortran main programs with
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DW_CC_program --- even when those functions use the standard
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calling conventions.
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Fortran, and before DWARF 4 DW_CC_program was the only
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piece of debugging information whose definition refers to
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a 'main program' at all, several compilers marked Fortran
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main programs with DW_CC_program --- even when those
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functions use the standard calling conventions.
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So until DWARF specifies a way to provide this information and
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compilers pick up the new representation, we'll support this
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practice. */
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Although DWARF now specifies a way to provide this
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information, we support this practice for backward
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compatibility. */
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if (DW_UNSND (&attr) == DW_CC_program
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&& cu->language == language_fortran
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&& part_die->name != NULL)
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set_objfile_main_name (objfile, part_die->name, language_fortran);
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&& cu->language == language_fortran)
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part_die->main_subprogram = 1;
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break;
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case DW_AT_inline:
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if (DW_UNSND (&attr) == DW_INL_inlined
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@ -15978,6 +15983,10 @@ read_partial_die (const struct die_reader_specs *reader,
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}
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break;
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case DW_AT_main_subprogram:
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part_die->main_subprogram = DW_UNSND (&attr);
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break;
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default:
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break;
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}
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@ -1,3 +1,8 @@
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2016-12-02 Tom Tromey <tom@tromey.com>
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* gdb.dwarf2/main-subprogram.c: New file.
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* gdb.dwarf2/main-subprogram.exp: New file.
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2016-12-01 Luis Machado <lgustavo@codesourcery.com>
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* gdb.base/maint.exp: Remove timeout handling for gdb_test_multiple.
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@ -0,0 +1,29 @@
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/* This testcase is part of GDB, the GNU debugger.
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Copyright 2016 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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int
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mymain ()
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{
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asm ("mymain_label: .globl mymain_label");
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return 0;
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}
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int
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main()
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{
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return mymain ();
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}
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@ -0,0 +1,73 @@
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# Copyright 2016 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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load_lib dwarf.exp
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# This test can only be run on targets which support DWARF-4 and use gas.
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if {![dwarf2_support]} {
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return 0
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}
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standard_testfile main-subprogram.c enum-type-dw.S
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# Make some DWARF for the test.
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set asm_file [standard_output_file $srcfile2]
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Dwarf::assemble $asm_file {
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global srcdir subdir srcfile
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set range [function_range mymain ${srcdir}/${subdir}/${srcfile}]
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set mymain_start [lindex $range 0]
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set mymain_length [lindex $range 1]
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cu {} {
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DW_TAG_compile_unit {
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{DW_AT_language @DW_LANG_C}
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{DW_AT_name main-subprogram.c}
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{DW_AT_comp_dir /tmp}
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} {
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declare_labels type
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type: DW_TAG_base_type {
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{DW_AT_byte_size 4 DW_FORM_sdata}
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{DW_AT_encoding @DW_ATE_signed}
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{DW_AT_name int}
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}
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DW_TAG_subprogram {
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{name mymain}
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{low_pc $mymain_start addr}
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{high_pc "$mymain_start + $mymain_length" addr}
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{type :$type}
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{DW_AT_main_subprogram 1 flag}
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} {
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}
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}
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}
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}
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if {[prepare_for_testing ${testfile}.exp ${testfile} \
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[list $srcfile $asm_file] {nodebug}]} {
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return -1
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}
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# Test that the "start" command stops in the "mymain" function.
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# This should happen because we used DW_AT_main_subprogram to tell gdb
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# that this was the real "main".
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if {[gdb_start_cmd] < 0} {
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untested "could not start ${testfile}"
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return -1
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}
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gdb_test "" "Temporary breakpoint .* mymain.*" "stopped at mymain"
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