[PATCH, testsuite] Fix gdb.cp/nsalias.exp issues

[Luis Machado <lgustavo@codesourcery.com>]

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Hi,

I've been chasing failures on gdb.cp/nsalias.exp for MIPS, but the 
strange thing is that the failures only reproduced with a GDB built 
without optimization.

Upon further investigation, i noticed the testcase was generating 
DW_AT_high_pc and DW_AT_low_pc entries with type DW_FORM_string, which 
is wrong.

GDB was using that information to load data as strings, and then 
proceeded to use the string pointers as addresses.

Even then, the test was passing just fine, because we were lucky enough 
to have the low_pc string pointer smaller than the high_pc string pointer.

The following patch fixes two issues. The first one is the 
DW_FORM_string type. The second one is adjusting the addresses so that 
they are non-zero, since GDB doesn't like seeing 0 in these fields due 
to a check contained in dwarf2_get_pc_bounds:

   if (low == 0 && !dwarf2_per_objfile->has_section_at_zero)
     return 0;

With both fixes, the testcase passes deterministically, and the failures 
i saw for the MIPS case were bad luck with the pointer comparisons.

OK?

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2014-06-18  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.cp/nsalias.exp: Set type of low_pc and high_pc entries
	to DW_FORM_addr and use non-zero addresses.

diff --git a/gdb/testsuite/gdb.cp/nsalias.exp b/gdb/testsuite/gdb.cp/nsalias.exp
index f99b609..1179c1c 100644
--- a/gdb/testsuite/gdb.cp/nsalias.exp
+++ b/gdb/testsuite/gdb.cp/nsalias.exp
@@ -153,20 +153,20 @@ Dwarf::assemble $asm_file {
 
 	    subprogram {
 		{specification :$im_foo_label}
-		{low_pc 0x0}
-		{high_pc 0x1}
+		{low_pc 0x1 DW_FORM_addr }
+		{high_pc 0x2 DW_FORM_addr }
 	    }
 
 	    subprogram {
 		{specification :$i_foo_label}
-		{low_pc 0x2}
-		{high_pc 0x3}
+		{low_pc 0x3 DW_FORM_addr }
+		{high_pc 0x4 DW_FORM_addr }
 	    }
 
 	    subprogram {
 		{specification :$o_foo_label}
-		{low_pc 0x4}
-		{high_pc 0x5}
+		{low_pc 0x5 DW_FORM_addr }
+		{high_pc 0x6 DW_FORM_addr }
 	    }
 	}
     }