gdb: Fix issue with Clang CLI macros

Clang up to version 15 (current) adds macros that were defined in the
command line or by "other means", according to the Dwarf specification,
after the last DW_MACRO_end_file, instead of before the first
DW_MACRO_start_file, as the specification dictates.  When GDB reads the
macros after the last file is closed, the macros never end up "in scope"
and so we can't print them.  This has been submitted as a bug to Clang
developers (https://github.com/llvm/llvm-project/issues/54506), and PR
macros/29034 was opened for GDB to keep track of this.

Seeing as there is no expected date for it to be fixed, add a workaround
for all current versions of Clang.  The workaround detects when
the main file would be closed and if the producer is Clang, and turns
that operation into a noop, so we keep a reference to the current_file
as those macros are read.

A test case was added to confirm the functionality, and the KFAIL for
running gdb.base/macro-source-path when using clang.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29034
Approved-By: Simon Marchi <simon.marchi@efficios.com>

2 files changed, 118 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.dwarf2/clang-cli-macro.c b/gdb/testsuite/gdb.dwarf2/clang-cli-macro.c
new file mode 100644
index 00000000000..749bcc1580e
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/clang-cli-macro.c
@@ -0,0 +1,20 @@
+/* Copyright 2022 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/>.  */
+
+int
+main (void)
+{
+  asm ("main_label: .globl main_label");
+}
diff --git a/gdb/testsuite/gdb.dwarf2/clang-cli-macro.exp b/gdb/testsuite/gdb.dwarf2/clang-cli-macro.exp
new file mode 100644
index 00000000000..41f786f57de
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/clang-cli-macro.exp
@@ -0,0 +1,98 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2022 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/>.
+
+# Clang has this bug where it puts the macros defined on the command-line
+# after the main file portion (see PR 29034 and
+# https://github.com/llvm/llvm-project/issues/54506 )
+# Test that GDB is still able to print macros in clang versions that
+# have this bug.
+
+load_lib dwarf.exp
+
+if {![dwarf2_support]} {
+    return 0
+}
+if {![test_compiler_info gcc-*-*]} {
+    untested "dwarf assembler needs GCC"
+}
+
+standard_testfile .c .S
+
+lassign [function_range main $srcdir/$subdir/$srcfile] \
+    main_start main_len
+
+set asm_file [standard_output_file $srcfile2]
+
+Dwarf::assemble $asm_file {
+    declare_labels L cu_macros
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_producer "clang version 15.0.0"}
+	    {DW_AT_language @DW_LANG_C11}
+	    {DW_AT_name $::srcfile}
+	    {DW_AT_macros $cu_macros DW_FORM_sec_offset}
+	    {DW_AT_stmt_list $L DW_FORM_sec_offset}
+	} {
+	    declare_labels int_type
+
+	    int_type: DW_TAG_base_type {
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+		{DW_AT_encoding  @DW_ATE_signed}
+		{DW_AT_name int}
+	    }
+	    DW_TAG_subprogram {
+		{MACRO_AT_func {main}}
+		{type :$int_type}
+	    }
+	}
+    }
+    lines {version 2} L {
+	file_name $::srcfile 1
+	program {
+	    DW_LNE_set_address $::main_start
+	    line 10
+	    DW_LNS_copy
+	    DW_LNE_set_address "$::main_start + $::main_len"
+	    DW_LNE_end_sequence
+	}
+    }
+
+    # Define the .debug_macro section.
+    macro {
+	cu_macros: unit {
+	    "debug-line-offset-label" $L
+	} {
+	    start_file 0 1
+		# A macro defined at line 1 of the main file.
+		define 1 "TWO 2"
+	    end_file
+	    define 0 "ONE 1"
+	}
+    }
+}
+
+if {[prepare_for_testing "failed to prepare" $testfile [list $srcfile $asm_file] {nodebug}]} {
+    return
+}
+
+if {![runto_main]} {
+    return
+}
+
+gdb_test "print TWO" "= 2" "print simple macro"
+gdb_test "print ONE" "= 1" "print defined from CLI"