Re: [PATCH] Include minimal symbol flavour name in LOC_UNRESOLVED error message.

[Doug Evans <xdje42 at gmail dot com>]

Nick Clifton <nickc@redhat.com> writes:
> Hi Doug,
>
>> 2015-08-29  Doug Evans  <xdje42@gmail.com>
>>
>> 	bfd/
>> 	* targets.c (enum bfd_flavour): Add comment.
>> 	(bfd_flavour_name): New function.
>> 	* bfd-in2.h: Regenerate.
>
> This part of the patch is approved.
>
> Cheers
>   Nick

Hi Nick.

Here is what I committed.
It includes the change suggested here:
https://sourceware.org/ml/gdb-patches/2015-08/msg00850.html

2015-09-18  Doug Evans  <xdje42@gmail.com>

	bfd/
	* targets.c (enum bfd_flavour): Add comment.
	(bfd_flavour_name): New function.
	* bfd-in2.h: Regenerate.

	gdb/
	* findvar.c (default_read_var_value) <LOC_UNRESOLVED>: Include the
	kind of minimal symbol in the error message.
	* objfiles.c (objfile_flavour_name): New function.
	* objfiles.h (objfile_flavour_name): Declare.

	gdb/testsuite/
	* gdb.dwarf2/dw2-bad-unresolved.c: New file.
	* gdb.dwarf2/dw2-bad-unresolved.exp: New file.

diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index 51fa54f..f06d76e 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -6980,6 +6980,7 @@ bfd_boolean generic_core_file_matches_executable_p
 
 enum bfd_flavour
 {
+  /* N.B. Update bfd_flavour_name if you change this.  */
   bfd_target_unknown_flavour,
   bfd_target_aout_flavour,
   bfd_target_coff_flavour,
@@ -7399,6 +7400,8 @@ const bfd_target *bfd_search_for_target
    (int (*search_func) (const bfd_target *, void *),
     void *);
 
+const char *bfd_flavour_name (enum bfd_flavour flavour);
+
 /* Extracted from format.c.  */
 bfd_boolean bfd_check_format (bfd *abfd, bfd_format format);
 
diff --git a/bfd/targets.c b/bfd/targets.c
index 1ada260..cc9d083 100644
--- a/bfd/targets.c
+++ b/bfd/targets.c
@@ -144,6 +144,7 @@ DESCRIPTION
 
 .enum bfd_flavour
 .{
+.  {* N.B. Update bfd_flavour_name if you change this.  *}
 .  bfd_target_unknown_flavour,
 .  bfd_target_aout_flavour,
 .  bfd_target_coff_flavour,
@@ -1829,3 +1830,50 @@ bfd_search_for_target (int (*search_func) (const bfd_target *, void *),
 
   return NULL;
 }
+
+/*
+FUNCTION
+	bfd_flavour_name
+
+SYNOPSIS
+	const char *bfd_flavour_name (enum bfd_flavour flavour);
+
+DESCRIPTION
+	Return the string form of @var{flavour}.
+*/
+
+const char *
+bfd_flavour_name (enum bfd_flavour flavour)
+{
+  switch (flavour)
+    {
+    case bfd_target_unknown_flavour: return "unknown file format";
+    case bfd_target_aout_flavour: return "a.out";
+    case bfd_target_coff_flavour: return "COFF";
+    case bfd_target_ecoff_flavour: return "ECOFF";
+    case bfd_target_xcoff_flavour: return "XCOFF";
+    case bfd_target_elf_flavour: return "ELF";
+    case bfd_target_ieee_flavour: return "IEEE";
+    case bfd_target_nlm_flavour: return "NLM";
+    case bfd_target_oasys_flavour: return "Oasys";
+    case bfd_target_tekhex_flavour: return "Tekhex";
+    case bfd_target_srec_flavour: return "Srec";
+    case bfd_target_verilog_flavour: return "Verilog";
+    case bfd_target_ihex_flavour: return "Ihex";
+    case bfd_target_som_flavour: return "SOM";
+    case bfd_target_os9k_flavour: return "OS9K";
+    case bfd_target_versados_flavour: return "Versados";
+    case bfd_target_msdos_flavour: return "MSDOS";
+    case bfd_target_ovax_flavour: return "Ovax";
+    case bfd_target_evax_flavour: return "Evax";
+    case bfd_target_mmo_flavour: return "MMO";
+    case bfd_target_mach_o_flavour: return "MACH_O";
+    case bfd_target_pef_flavour: return "PEF";
+    case bfd_target_pef_xlib_flavour: return "PEF_XLIB";
+    case bfd_target_sym_flavour: return "SYM";
+    /* There is no "default" case here so that -Wswitch (part of -Wall)
+       catches missing entries.  */
+    }
+
+  abort ();
+}
diff --git a/gdb/findvar.c b/gdb/findvar.c
index fd1b9d7..11325cf 100644
--- a/gdb/findvar.c
+++ b/gdb/findvar.c
@@ -737,8 +737,20 @@ default_read_var_value (struct symbol *var, const struct block *var_block,
 	   symbol_objfile (var));
 	msym = lookup_data.result.minsym;
 
+	/* If we can't find the minsym there's a problem in the symbol info.
+	   The symbol exists in the debug info, but it's missing in the minsym
+	   table.  */
 	if (msym == NULL)
-	  error (_("No global symbol \"%s\"."), SYMBOL_LINKAGE_NAME (var));
+	  {
+	    const char *flavour_name
+	      = objfile_flavour_name (symbol_objfile (var));
+
+	    /* We can't get here unless we've opened the file, so flavour_name
+	       can't be NULL.  */
+	    gdb_assert (flavour_name != NULL);
+	    error (_("Missing %s symbol \"%s\"."),
+		   flavour_name, SYMBOL_LINKAGE_NAME (var));
+	  }
 	obj_section = MSYMBOL_OBJ_SECTION (lookup_data.result.objfile, msym);
 	/* Relocate address, unless there is no section or the variable is
 	   a TLS variable. */
diff --git a/gdb/objfiles.c b/gdb/objfiles.c
index 907126c..f6be91e 100644
--- a/gdb/objfiles.c
+++ b/gdb/objfiles.c
@@ -1614,6 +1614,16 @@ objfile_debug_name (const struct objfile *objfile)
   return lbasename (objfile->original_name);
 }
 
+/* See objfiles.h.  */
+
+const char *
+objfile_flavour_name (struct objfile *objfile)
+{
+  if (objfile->obfd != NULL)
+    return bfd_flavour_name (bfd_get_flavour (objfile->obfd));
+  return NULL;
+}
+
 /* Provide a prototype to silence -Wmissing-prototypes.  */
 extern initialize_file_ftype _initialize_objfiles;
 
diff --git a/gdb/objfiles.h b/gdb/objfiles.h
index be2a5ef..da5ac1a 100644
--- a/gdb/objfiles.h
+++ b/gdb/objfiles.h
@@ -744,6 +744,11 @@ const char *objfile_filename (const struct objfile *objfile);
 
 extern const char *objfile_debug_name (const struct objfile *objfile);
 
+/* Return the name of the file format of OBJFILE if the file has been opened,
+   otherwise return NULL.  */
+
+const char *objfile_flavour_name (struct objfile *objfile);
+
 /* Set the objfile's notion of the "main" name and language.  */
 
 extern void set_objfile_main_name (struct objfile *objfile,
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bad-unresolved.c b/gdb/testsuite/gdb.dwarf2/dw2-bad-unresolved.c
new file mode 100644
index 0000000..1c35510
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bad-unresolved.c
@@ -0,0 +1,24 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 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;
+}
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bad-unresolved.exp b/gdb/testsuite/gdb.dwarf2/dw2-bad-unresolved.exp
new file mode 100644
index 0000000..85c4ebb
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bad-unresolved.exp
@@ -0,0 +1,59 @@
+# Copyright 2015 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/>.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0  
+}
+
+standard_testfile dw2-bad-unresolved.c dw2-bad-unresolved-2.S
+
+# Set up the DWARF for the test.
+# The key part of this is the definition of variable "var" having no location.
+# That will cause it to have LOC_UNRESOLVED.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_language @DW_LANG_C}
+	    {DW_AT_name     dw2-bad-unresolved-2.c}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels b_l
+
+	    b_l: DW_TAG_base_type {
+		{DW_AT_byte_size 1 DW_FORM_sdata}
+		{DW_AT_encoding  @DW_ATE_signed}
+		{DW_AT_name      bool}
+	    }
+	    DW_TAG_variable {
+		{name var}
+		{type :$b_l}
+		{external 1 flag}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+	  [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+gdb_test "ptype var" "type = bool"
+gdb_test "print var" "Missing .* symbol \"var\"."