Add dw2-aranges.exp

This test checks that GDB is able to load DWARF information when
.debug_aranges has a section address size that is set to 0.

This test was originally written by Jan Kratochvil to test commit
927aa2e778 from 2017, titled "DWARF-5: .debug_names index consumer".

This test was originally written using a static .S file and has
been present in the Fedora tree for a long time.

If dwarf2/aranges.c is modified to turn off the address_size check,
GDB will crash with SIGFPE when loading the executable with address
size set to zero.

I modified the DWARF assembler to make it possible to set the address
size to zero in a .debug_aranges section and used the DWARF assembler
to produce the assembly file.

Co-Authored-By: Jan Kratochvil <jan.kratochvil@redhat.com>
Approved-by: Kevin Buettner <kevinb@redhat.com>

gdb/testsuite/gdb.dwarf2/dw2-aranges.c

@@ -0,0 +1,24 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2024 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 <http://www.gnu.org/licenses/>.  */
+
+/* Dummy main function.  */
+
+int
+main (void)
+{
+  return 0;
+}

gdb/testsuite/gdb.dwarf2/dw2-aranges.exp

@@ -0,0 +1,40 @@
+# Copyright 2004-2024 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 <http://www.gnu.org/licenses/>.
+
+# Test .debug_aranges containing zero address_size.
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+# For now pick a sampling of likely targets.
+load_lib dwarf.exp
+require dwarf2_support
+
+standard_testfile .c -2.S
+set asm_file [standard_output_file $srcfile2]
+
+Dwarf::assemble $asm_file {
+    cu { label cu_start } {
+	compile_unit {{language @DW_LANG_C}} {
+	}
+    }
+    aranges { addr_zero true } cu_start {
+    }
+}
+
+if { [prepare_for_testing "failed to prepare" $binfile  [list $asm_file $srcfile ]] } {
+    return -1
+}
+
+# Failed gdb_load would abort the testcase execution earlier.
+pass "file loaded"

gdb/testsuite/lib/dwarf.exp

@@ -2759,8 +2759,11 @@ namespace eval Dwarf {
 	    set addr_op .4byte
 	}
 
-	_op $addr_op $arange_start "Address range start$comment"
-	_op $addr_op $arange_length "Address range length$comment"
+	# Do not emit address ranges when the Address size is set to 0.
+	if { $_addr_size > 0 } {
+	    _op $addr_op $arange_start "Address range start$comment"
+	    _op $addr_op $arange_length "Address range length$comment"
+	}
     }
 
     # Emit a DWARF .debug_aranges unit.
@@ -2797,6 +2800,7 @@ namespace eval Dwarf {
 	    { cu_is_64 0 }
 	    { section_version 2 }
 	    { seg_size 0 }
+	    { addr_zero false }
 	}
 	set _seg_size $seg_size
 
@@ -2806,6 +2810,10 @@ namespace eval Dwarf {
 	    set _addr_size 4
 	}
 
+	if { $addr_zero } {
+	    set _addr_size 0
+	}
+
 	# Switch to .debug_aranges section.
 	_section .debug_aranges
 
@@ -2853,6 +2861,9 @@ namespace eval Dwarf {
 
 	# Padding.
 	set tuple_size [expr 2 * $_addr_size + $_seg_size]
+	if {$tuple_size == 0} {
+	    set tuple_size 1
+	}
 	while { 1 } {
 	    if { [expr $offset % $tuple_size] == 0 } {
 		break