[gdb/exp] Fix exception when printing optimized out vla

When compiling vla-optimized-out.c with -O3 and a recent gcc, and trying to
print the vla a in f1, we run into this gdb exception:
...
Cannot find matching parameter at DW_TAG_call_site 0x4003be at main
...

This is a regression introduced by 42dc7699a2 "[gdb/exp] Fix printing of type
of optimized out vla".

This patch fixes the regression by wrapping the ctx.eval call in
dwarf2_locexpr_baton_eval in try/catch, similar to what is done in
dwarf2_evaluate_loc_desc_full.

Build and reg-tested on x86_64-linux.

2018-07-25  Tom de Vries  <tdevries@suse.de>

	* dwarf2loc.c (dwarf2_locexpr_baton_eval): Wrap ctx.eval call in
	try/catch.

	* gdb.base/vla-optimized-out-o3.exp: New file.  Reuse
	vla-optimized-out.c.

1 files changed, 20 insertions, 1 deletions

diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c
index 730934f..a98b676 100644
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -2573,7 +2573,26 @@ dwarf2_locexpr_baton_eval (const struct dwarf2_locexpr_baton *dlbaton,
   ctx.ref_addr_size = dwarf2_per_cu_ref_addr_size (dlbaton->per_cu);
   ctx.offset = dwarf2_per_cu_text_offset (dlbaton->per_cu);
 
-  ctx.eval (dlbaton->data, dlbaton->size);
+  TRY
+    {
+      ctx.eval (dlbaton->data, dlbaton->size);
+    }
+  CATCH (ex, RETURN_MASK_ERROR)
+    {
+      if (ex.error == NOT_AVAILABLE_ERROR)
+	{
+	  return 0;
+	}
+      else if (ex.error == NO_ENTRY_VALUE_ERROR)
+	{
+	  if (entry_values_debug)
+	    exception_print (gdb_stdout, ex);
+	  return 0;
+	}
+      else
+	throw_exception (ex);
+    }
+  END_CATCH
 
   switch (ctx.location)
     {