gdb.dwarf2: Define and use gdb_target_symbol for symbol prefixes

Some of the tests in gdb.dwarf2 which use Dwarf::assemble refer to
(minimal/linker) symbols created in the course of building a small
test program.  Some targets use a prefix such as underscore ("_") on
these symbols.  Many of the tests in gdb.dwarf2 do not take this into
account.  As a consequence, these tests fail to build, resulting
either in failures or untested testcases.

Here is an example from gdb.dwarf2/dw2-regno-invalid.exp:

    Dwarf::assemble $asm_file {
        cu {} {
            compile_unit {
                {low_pc main DW_FORM_addr}
                {high_pc main+0x10000 DW_FORM_addr}
            } {
            ...
            }

For targets which require an underscore prefix on linker symbols,
the two occurrences of "main" would have to have a prepended underscore,
i.e. _main instead of main.

For the above case, a call to the new proc gdb_target_symbol is used
prepend the correct prefix to the symbol.  I.e. the above code is
rewritten (as shown in the patch) as follows:

    Dwarf::assemble $asm_file {
        cu {} {
            compile_unit {
                {low_pc [gdb_target_symbol main] DW_FORM_addr}
                {high_pc [gdb_target_symbol main]+0x10000 DW_FORM_addr}
            } {
            ...
            }

I also found it necessary to make an adjustment to lib/dwarf.exp so that
expressions of more than just one list element can be used in DW_TAG_...
constructs.  Both atomic-type.exp and dw2-bad-mips-linkage-name.exp require
this new functionality.

gdb/testsuite/ChangeLog:

	* lib/gdb.exp (gdb_target_symbol_prefix, gdb_target_symbol):
	New procs.
	* lib/dwarf.exp (_handle_DW_TAG): Handle attribute values,
	representing expressions, of more than one list element.
	* gdb.dwarf2/atomic-type.exp (Dwarf::assemble): Use gdb_target_symbol
	to prepend linker symbol prefix to f.
	* gdb.dwarf2/data-loc.exp (Dwarf::assemble): Likewise, for
	table_1 and table_2.
	* gdb.dwarf2/dw2-bad-mips-linkage-name.exp (Dwarf::assemble):
	Likewise, for f and g.
	* gdb.dwarf2/dw2-ifort-parameter.exp (Dwarf::assemble): Likewise,
	for ptr.
	* gdb.dwarf2/dw2-regno-invalid.exp (Dwarf::assemble): Likewise,
	for main.
	* gdb.dwarf2/dynarr-ptr.exp (Dwarf::assemble): Likewise, for
	table_1_ptr and table_2_ptr.

2 files changed, 61 insertions, 2 deletions

diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp
index 5dc7ea8..9716795 100644
--- a/gdb/testsuite/lib/dwarf.exp
+++ b/gdb/testsuite/lib/dwarf.exp
@@ -621,7 +621,18 @@ namespace eval Dwarf {
 
 	foreach attr $attrs {
 	    set attr_name [_map_name [lindex $attr 0] _AT]
-	    set attr_value [uplevel 2 [list subst [lindex $attr 1]]]
+
+	    # When the length of ATTR is greater than 2, the last
+	    # element of the list must be a form.  The second through
+	    # the penultimate elements are joined together and
+	    # evaluated using subst.  This allows constructs such as
+	    # [gdb_target_symbol foo] to be used.
+
+	    if {[llength $attr] > 2} {
+	        set attr_value [uplevel 2 [list subst [join [lrange $attr 1 end-1]]]]
+	    } else {
+	        set attr_value [uplevel 2 [list subst [lindex $attr 1]]]
+	    }
 
 	    if { [string equal "MACRO_AT_func" $attr_name] } {
 		_handle_macro_at_func $attr_value
@@ -629,7 +640,7 @@ namespace eval Dwarf {
 		_handle_macro_at_range $attr_value
 	    } else {
 		if {[llength $attr] > 2} {
-		    set attr_form [lindex $attr 2]
+		    set attr_form [lindex $attr end]
 		} else {
 		    # If the value looks like an integer, a form is required.
 		    if [string is integer $attr_value] {
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 6681a49..83dd0a2 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -5523,6 +5523,54 @@ proc core_find {binfile {deletefiles {}} {arg ""}} {
     return $destcore
 }
 
+# gdb_target_symbol_prefix compiles a test program and then examines
+# the output from objdump to determine the prefix (such as underscore)
+# for linker symbol prefixes.
+
+gdb_caching_proc gdb_target_symbol_prefix {
+    # Set up and compile a simple test program...
+    set src [standard_temp_file main[pid].c]
+    set exe [standard_temp_file main[pid].x]
+
+    gdb_produce_source $src {
+	int main() {
+	    return 0;
+	}
+    }
+
+    verbose "compiling testfile $src" 2
+    set compile_flags {debug nowarnings quiet}
+    set lines [gdb_compile $src $exe executable $compile_flags]
+
+    set prefix ""
+
+    if ![string match "" $lines] then {
+        verbose "gdb_target_symbol_prefix: testfile compilation failed, returning null prefix" 2
+    } else {
+	set objdump_program [gdb_find_objdump]
+	set result [catch "exec $objdump_program --syms $exe" output]
+
+	if { $result == 0 \
+	     && ![regexp -lineanchor \
+	          { ([^ a-zA-Z0-9]*)main$} $output dummy prefix] } {
+	    verbose "gdb_target_symbol_prefix: Could not find main in objdump output; returning null prefix" 2
+	}
+    }
+
+    file delete $src
+    file delete $exe
+
+    return $prefix
+}
+
+# gdb_target_symbol returns the provided symbol with the correct prefix
+# prepended.  (See gdb_target_symbol_prefix, above.)
+
+proc gdb_target_symbol { symbol } {
+  set prefix [gdb_target_symbol_prefix]
+  return "${prefix}${symbol}"
+}
+
 # gdb_target_symbol_prefix_flags returns a string that can be added
 # to gdb_compile options to define SYMBOL_PREFIX macro value
 # symbol_prefix_flags returns a string that can be added