From: Tom Tromey Date: Mon, 14 Nov 2016 03:56:34 +0000 (-0700) Subject: PR symtab/16264 - support DW_AT_main_subprogram X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=0c1b455e294c6debb4efedc7f1346f3c43249f15;p=binutils-gdb.git 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 PR symtab/16264: * dwarf2read.c (struct partial_die_info) : New member. (add_partial_symbol): Call set_objfile_main_name. (read_partial_die): Handle DW_AT_main_subprogram. : don't call set_objfile_main_name, but set main_subprogram flag. 2016-12-02 Tom Tromey * gdb.dwarf2/main-subprogram.c: New file. * gdb.dwarf2/main-subprogram.exp: New file. --- diff --git a/gdb/ChangeLog b/gdb/ChangeLog index fa02377a3a6..33d824304f3 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,13 @@ +2016-12-02 Tom Tromey + + PR symtab/16264: + * dwarf2read.c (struct partial_die_info) : New + member. + (add_partial_symbol): Call set_objfile_main_name. + (read_partial_die): Handle DW_AT_main_subprogram. + : don't call set_objfile_main_name, but + set main_subprogram flag. + 2016-12-02 Simon Marchi * tracefile-tfile.c (tfile_write_status): Adjust to renames. diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c index 558159aedad..ed10e03812f 100644 --- a/gdb/dwarf2read.c +++ b/gdb/dwarf2read.c @@ -1105,6 +1105,9 @@ struct partial_die_info unsigned int has_pc_info : 1; unsigned int may_be_inlined : 1; + /* This DIE has been marked DW_AT_main_subprogram. */ + unsigned int main_subprogram : 1; + /* Flag set if the SCOPE field of this structure has been computed. */ unsigned int scope_set : 1; @@ -6930,6 +6933,9 @@ add_partial_symbol (struct partial_die_info *pdi, struct dwarf2_cu *cu) &objfile->static_psymbols, addr, cu->language, objfile); } + + if (pdi->main_subprogram && actual_name != NULL) + set_objfile_main_name (objfile, actual_name, cu->language); break; case DW_TAG_constant: { @@ -15949,19 +15955,18 @@ read_partial_die (const struct die_reader_specs *reader, to describe functions' calling conventions. However, because it's a necessary piece of information in - Fortran, and because DW_CC_program is the only piece of debugging - information whose definition refers to a 'main program' at all, - several compilers have begun marking Fortran main programs with - DW_CC_program --- even when those functions use the standard - calling conventions. - - So until DWARF specifies a way to provide this information and - compilers pick up the new representation, we'll support this - practice. */ + Fortran, and before DWARF 4 DW_CC_program was the only + piece of debugging information whose definition refers to + a 'main program' at all, several compilers marked Fortran + main programs with DW_CC_program --- even when those + functions use the standard calling conventions. + + Although DWARF now specifies a way to provide this + information, we support this practice for backward + compatibility. */ if (DW_UNSND (&attr) == DW_CC_program - && cu->language == language_fortran - && part_die->name != NULL) - set_objfile_main_name (objfile, part_die->name, language_fortran); + && cu->language == language_fortran) + part_die->main_subprogram = 1; break; case DW_AT_inline: if (DW_UNSND (&attr) == DW_INL_inlined @@ -15978,6 +15983,10 @@ read_partial_die (const struct die_reader_specs *reader, } break; + case DW_AT_main_subprogram: + part_die->main_subprogram = DW_UNSND (&attr); + break; + default: break; } diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 0ec07ae3af3..0e06d9ef809 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2016-12-02 Tom Tromey + + * gdb.dwarf2/main-subprogram.c: New file. + * gdb.dwarf2/main-subprogram.exp: New file. + 2016-12-01 Luis Machado * gdb.base/maint.exp: Remove timeout handling for gdb_test_multiple. diff --git a/gdb/testsuite/gdb.dwarf2/main-subprogram.c b/gdb/testsuite/gdb.dwarf2/main-subprogram.c new file mode 100644 index 00000000000..97ca22e713c --- /dev/null +++ b/gdb/testsuite/gdb.dwarf2/main-subprogram.c @@ -0,0 +1,29 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2016 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +int +mymain () +{ + asm ("mymain_label: .globl mymain_label"); + return 0; +} + +int +main() +{ + return mymain (); +} diff --git a/gdb/testsuite/gdb.dwarf2/main-subprogram.exp b/gdb/testsuite/gdb.dwarf2/main-subprogram.exp new file mode 100644 index 00000000000..08c076b1096 --- /dev/null +++ b/gdb/testsuite/gdb.dwarf2/main-subprogram.exp @@ -0,0 +1,73 @@ +# Copyright 2016 Free Software Foundation, Inc. + +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . +load_lib dwarf.exp + +# This test can only be run on targets which support DWARF-4 and use gas. +if {![dwarf2_support]} { + return 0 +} + +standard_testfile main-subprogram.c enum-type-dw.S + +# Make some DWARF for the test. +set asm_file [standard_output_file $srcfile2] +Dwarf::assemble $asm_file { + global srcdir subdir srcfile + + set range [function_range mymain ${srcdir}/${subdir}/${srcfile}] + set mymain_start [lindex $range 0] + set mymain_length [lindex $range 1] + + cu {} { + DW_TAG_compile_unit { + {DW_AT_language @DW_LANG_C} + {DW_AT_name main-subprogram.c} + {DW_AT_comp_dir /tmp} + } { + declare_labels type + + type: DW_TAG_base_type { + {DW_AT_byte_size 4 DW_FORM_sdata} + {DW_AT_encoding @DW_ATE_signed} + {DW_AT_name int} + } + + DW_TAG_subprogram { + {name mymain} + {low_pc $mymain_start addr} + {high_pc "$mymain_start + $mymain_length" addr} + {type :$type} + {DW_AT_main_subprogram 1 flag} + } { + } + } + } +} + +if {[prepare_for_testing ${testfile}.exp ${testfile} \ + [list $srcfile $asm_file] {nodebug}]} { + return -1 +} + +# Test that the "start" command stops in the "mymain" function. +# This should happen because we used DW_AT_main_subprogram to tell gdb +# that this was the real "main". + +if {[gdb_start_cmd] < 0} { + untested "could not start ${testfile}" + return -1 +} + +gdb_test "" "Temporary breakpoint .* mymain.*" "stopped at mymain"