Properly intern constants into psymtab

Variables with a DW_AT_const_value but without a DW_AT_location were not
getting added to the partial symbol table.  They are added to the full
symbol table, however, when the compilation unit's psymtabs are
expanded.

Before:

   (gdb) p one
   No symbol "one" in current context.
   (gdb) mt flush-symbol-cache
   (gdb) mt expand one.c
   (gdb) p one
   $1 = 1

After:

   (gdb) p one
   $1 = 1

To the user it's pretty strange, as depending on whether tab completion
has forced expansion of all CUs or not the lookup might succeed, or not
if the failure was already added to the symbol cache.

This commit simply makes sure to add constants to the partial symbol
tables.

gdb/testsuite/ChangeLog:

	PR symtab/18148
	* gdb.dwarf2/dw2-intercu.S (one, two): Add variables that have a
	const_value but not a location.
	* gdb.dwarf2/dw2-intercu.exp: Add tests that constants without
	location defined in non-main CUs are visible.

gdb/ChangeLog:

	PR symtab/18148
	* dwarf2read.c (struct partial_die_info): Add has_const_value
	member.
	(add_partial_symbol): Don't punt on symbols that have const_value
	attributes.
	(read_partial_die): Detect DW_AT_const_value.

2 files changed, 84 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-intercu.S b/gdb/testsuite/gdb.dwarf2/dw2-intercu.S
index b155e0b..c033e4d 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-intercu.S
+++ b/gdb/testsuite/gdb.dwarf2/dw2-intercu.S
@@ -64,6 +64,24 @@ func_cu1:
 	.byte		1			/* DW_AT_frame_base: length */
 	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
 
+	/* This type is named "int1" and not "int" to ensure it is unique,
+	   and thus we can easily ensure we expand this CU and not some
+	   other CU with "int".  */
+.Ltype_int1_in_cu1:
+	.uleb128	3			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int1\0"		/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+.Ltype_const_int1_in_cu1:
+	.uleb128	4			/* Abbrev: DW_TAG_const_type */
+	.4byte		 .Ltype_int1_in_cu1-.Lcu1_begin /* DW_AT_type */
+
+	.uleb128	5			/* Abbrev: DW_TAG_variable */
+	.ascii		"one\0"			/* DW_AT_name */
+	.4byte		.Ltype_const_int1_in_cu1-.Lcu1_begin   /* DW_AT_type */
+	.byte		1			/* DW_AT_const_value */
+
 	.byte		0			/* End of children of CU */
 
 .Lcu1_end:
@@ -92,6 +110,15 @@ func_cu1:
 	.byte		4			/* DW_AT_byte_size */
 	.byte		5			/* DW_AT_encoding */
 
+.Ltype_const_int2_in_cu2:
+	.uleb128	3			/* Abbrev: DW_TAG_const_type */
+	.4byte		 .Ltype_int2_in_cu2-.Lcu2_begin /* DW_AT_type */
+
+	.uleb128	4			/* Abbrev: DW_TAG_variable */
+	.ascii		"two\0"			/* DW_AT_name */
+	.4byte		.Ltype_const_int2_in_cu2-.Lcu2_begin   /* DW_AT_type */
+	.byte		2			/* DW_AT_const_value */
+
 	.byte		0			/* End of children of CU */
 
 .Lcu2_end:
@@ -139,6 +166,38 @@ func_cu1:
 	.byte		0x0			/* Terminator */
 	.byte		0x0			/* Terminator */
 
+	.uleb128	3			/* Abbrev code */
+	.uleb128	0x24			/* DW_TAG_base_type */
+	.byte		0			/* has_children */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0xb			/* DW_AT_byte_size */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x3e			/* DW_AT_encoding */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	4			/* Abbrev code */
+	.uleb128	0x26			/* DW_TAG_const_type */
+	.byte		0x0			/* DW_children_no */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	5			/* Abbrev code */
+	.uleb128	0x34			/* DW_TAG_variable */
+	.byte		0x0			/* DW_children_no */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.uleb128	0x1c			/* DW_AT_const_value */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
 	.byte		0x0			/* Terminator */
 	.byte		0x0			/* Terminator */
 
@@ -167,6 +226,26 @@ func_cu1:
 	.byte		0x0			/* Terminator */
 	.byte		0x0			/* Terminator */
 
+	.uleb128	3			/* Abbrev code */
+	.uleb128	0x26			/* DW_TAG_const_type */
+	.byte		0x0			/* DW_children_no */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	4			/* Abbrev code */
+	.uleb128	0x34			/* DW_TAG_variable */
+	.byte		0x0			/* DW_children_no */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.uleb128	0x1c			/* DW_AT_const_value */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
 	.byte		0x0			/* Terminator */
 	.byte		0x0			/* Terminator */
 
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-intercu.exp b/gdb/testsuite/gdb.dwarf2/dw2-intercu.exp
index 8de99c5..eba791b 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-intercu.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-intercu.exp
@@ -42,3 +42,8 @@ gdb_test_no_output "set listsize 1"
 gdb_test "list func_cu1" "4\[ \t\]+File 1 Line 4"
 
 gdb_test "ptype func_cu1" "type = int2 \\(\\)"
+
+gdb_test "p one" "= 1"
+gdb_test "p two" "= 2"
+gdb_test "ptype one" "type = const int1"
+gdb_test "ptype two" "type = const int2"