[PATCH] gdb/disassembly: Update to handle non-statement addresses

[Andrew Burgess]

After the introduction of support for non-statement addresses in the
line table, the output for 'disassemble /m' can be broken in some
cases.

With the /m format disassembly GDB associates a set of addresses with
each line, these addresses are then sorted and printed for each line.

When the non-statement support was added GDB was incorrectly told to
ignore non-statement instructions, and not add these to the result
table.  This means that these instructions are completely missing from
the output.

This commit removes the code that caused non-statement lines to be
ignored.

A result of this change is that GDB will now potentially include new
line numbers in the 'disassembly /m' output, lines that previously
were only in the line table as non-statement lines will now appear in
the disassembly output.  This feels like an improvement though.

gdb/ChangeLog:

	* disasm.c (do_mixed_source_and_assembly_deprecated): Don't
	exclude non-statement entries.

gdb/testsuite/ChangeLog:

	* gdb.dwarf2/dw2-disasm-over-non-stmt.exp: New file.
---
 gdb/ChangeLog                                 |   5 +
 gdb/disasm.c                                  |   6 -
 gdb/testsuite/ChangeLog                       |   4 +
 .../gdb.dwarf2/dw2-disasm-over-non-stmt.exp   | 192 ++++++++++++++++++
 4 files changed, 201 insertions(+), 6 deletions(-)
 create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-disasm-over-non-stmt.exp

diff --git a/gdb/disasm.c b/gdb/disasm.c
index 143ba2f59b9..e45c8400689 100644
--- a/gdb/disasm.c
+++ b/gdb/disasm.c
@@ -376,12 +376,6 @@ do_mixed_source_and_assembly_deprecated
       if (le[i].line == le[i + 1].line && le[i].pc == le[i + 1].pc)
 	continue;		/* Ignore duplicates.  */
 
-      /* Ignore non-statement line table entries.  This means we print the
-	 source line at the place where GDB would insert a breakpoint for
-	 that line, which seems more intuitive.  */
-      if (le[i].is_stmt == 0)
-	continue;
-
       /* Skip any end-of-function markers.  */
       if (le[i].line == 0)
 	continue;
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-disasm-over-non-stmt.exp b/gdb/testsuite/gdb.dwarf2/dw2-disasm-over-non-stmt.exp
new file mode 100644
index 00000000000..6bcc5e77404
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-disasm-over-non-stmt.exp
@@ -0,0 +1,192 @@
+# Copyright 2020 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/>.
+
+# Create an example function that contains address marked as both
+# statements and non-statements then disassemble the function.
+#
+# Of particular interest is how 'disassemble /m' handles the
+# non-statement addresses, we want to ensure that these addresses are
+# included in the disassembly output.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+# The .c files use __attribute__.
+if [get_compiler_info] {
+    return -1
+}
+if !$gcc_compiled {
+    return 0
+}
+
+# Reuse many of the test source files from dw2-inline-header-1.exp.
+standard_testfile dw2-inline-header-lbls.c dw2-inline-header.S \
+    dw2-inline-header.c
+
+set build_options {nodebug optimize=-O1}
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global srcdir subdir srcfile srcfile3 testfile
+    upvar build_options build_options
+    upvar start_label start_label
+    declare_labels lines_label
+
+    get_func_info main $build_options
+
+    cu {} {
+	compile_unit {
+	    {producer "gcc" }
+	    {language @DW_LANG_C}
+	    {name ${srcfile3}}
+	    {low_pc 0 addr}
+	    {stmt_list ${lines_label} DW_FORM_sec_offset}
+	} {
+	    subprogram {
+		{external 1 flag}
+		{name main}
+		{low_pc $main_start addr}
+		{high_pc "$main_start + $main_len" addr}
+	    }
+	}
+    }
+
+    lines {version 2 default_is_stmt 1} lines_label {
+	include_dir "${srcdir}/${subdir}"
+	file_name "$srcfile3" 1
+
+	program {
+	    {DW_LNE_set_address line_label_1}
+	    {DW_LNS_advance_line 15}
+	    {DW_LNS_copy}
+
+	    {DW_LNE_set_address line_label_2}
+	    {DW_LNS_negate_stmt}
+	    {DW_LNS_copy}
+
+	    {DW_LNE_set_address line_label_3}
+	    {DW_LNS_advance_line 1}
+	    {DW_LNS_copy}
+
+	    {DW_LNE_set_address line_label_4}
+	    {DW_LNS_negate_stmt}
+	    {DW_LNS_copy}
+
+	    {DW_LNE_set_address line_label_5}
+	    {DW_LNS_negate_stmt}
+	    {DW_LNS_copy}
+
+	    {DW_LNE_set_address line_label_6}
+	    {DW_LNS_advance_line 1}
+	    {DW_LNS_negate_stmt}
+	    {DW_LNS_copy}
+
+	    {DW_LNE_set_address line_label_7}
+	    {DW_LNS_copy}
+	    {DW_LNE_end_sequence}
+	}
+    }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+	  [list $srcfile $asm_file] $build_options] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+# Now for the test.  Disassemble 'main' and split up the disassembly
+# output.  We build an associative array, for each line number store
+# the list of addresses that were part of its disassembly output.
+set linenum -1
+array set lines {}
+set addrs {}
+gdb_test_multiple "disassemble /m main" "" {
+    -re "Dump of assembler code for function main:\r\n" {
+	exp_continue
+    }
+
+    -re "^(\\d+)\\s+\[^\r\n\]+\r\n" {
+	if { $linenum != -1 } {
+	    set lines($linenum) $addrs
+	    set addrs {}
+	}
+	set linenum $expect_out(1,string)
+	exp_continue
+    }
+
+    -re "^(?:=>)?\\s*($hex)\\s*\[^\r\n\]+\r\n" {
+	set address $expect_out(1,string)
+	lappend addrs $address
+	exp_continue
+    }
+
+    -re "^\\s*\r\n" {
+	exp_continue
+    }
+
+    -re "^End of assembler dump\\.\r\n" {
+	if { $linenum != -1 } {
+	    set lines($linenum) $addrs
+	    set linenum -1
+	    set addrs {}
+	}
+	exp_continue
+    }
+
+    -re "^$gdb_prompt $" {
+	# All done.
+    }
+}
+
+# Look in the global LINES array and check that the disassembly for
+# line LINENUM included the address of LABEL.
+proc check_disassembly_results { linenum label } {
+    global lines
+
+    set address [get_hexadecimal_valueof "&${label}" "__unknown__"]
+    set testname "check_disassembly_results $linenum $label"
+    if {![info exists lines($linenum)]} {
+	fail "$testname (no disassembly for $linenum)"
+	return
+    }
+
+    # Use a loop to compare the addresses as the addresses extracted
+    # from the disassembly output can be padded with zeros, while the
+    # address of the label will not be padded.
+    set addrs $lines($linenum)
+    foreach a $addrs {
+	if { $a == $address } {
+	    pass $testname
+	    return
+	}
+    }
+    fail $testname
+}
+
+# Now check that each label we expect to be associated with each line
+# shows up in the disassembly output.
+check_disassembly_results 16 "line_label_1"
+check_disassembly_results 16 "line_label_2"
+check_disassembly_results 17 "line_label_3"
+check_disassembly_results 17 "line_label_4"
+check_disassembly_results 17 "line_label_5"
+check_disassembly_results 18 "line_label_6"
-- 
2.25.4