Fix "catch exception" with dynamic linking

When an Ada program is dynamically linked against libgnat, and when
one of the standard exceptions is used, the exception object may be
referenced by the main executable using a copy relocation.

In this situation, a "catch exception" for those exceptions will not
manage to stop.  This happens because, under the hood, "catch
exception" creates an expression object that examines the object
addresses -- but in this case, the address will be incorrect.

This patch fixes the problem by arranging for these filter expressions
to examine all the relevant minimal symbols.  This way, the object
from libgnat will be found as well.

Tested on x86-64 Fedora 29.

gdb/ChangeLog
2019-04-30  Tom Tromey  <tromey@adacore.com>

	* ada-lang.c (ada_lookup_simple_minsyms): New function.
	(create_excep_cond_exprs): Iterate over program spaces.
	(ada_exception_catchpoint_cond_string): Examine all minimal
	symbols for exception types.

gdb/testsuite/ChangeLog
2019-04-30  Tom Tromey  <tromey@adacore.com>

	* lib/ada.exp (find_ada_tool): New proc.
	* lib/gdb.exp (gdb_compile_shlib): Allow .o files as inputs.
	* gdb.ada/catch_ex_std.exp: New file.
	* gdb.ada/catch_ex_std/foo.adb: New file.
	* gdb.ada/catch_ex_std/some_package.adb: New file.
	* gdb.ada/catch_ex_std/some_package.ads: New file.

1 files changed, 83 insertions, 25 deletions

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 28ab931..676cd6d 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -63,6 +63,7 @@
 #include "common/function-view.h"
 #include "common/byte-vector.h"
 #include <algorithm>
+#include <map>
 
 /* Define whether or not the C operator '/' truncates towards zero for
    differently signed operands (truncation direction is undefined in C).
@@ -4949,6 +4950,36 @@ ada_lookup_simple_minsym (const char *name)
   return result;
 }
 
+/* Return all the bound minimal symbols matching NAME according to Ada
+   decoding rules.  Returns an empty vector if there is no such
+   minimal symbol.  Names prefixed with "standard__" are handled
+   specially: "standard__" is first stripped off, and only static and
+   global symbols are searched.  */
+
+static std::vector<struct bound_minimal_symbol>
+ada_lookup_simple_minsyms (const char *name)
+{
+  std::vector<struct bound_minimal_symbol> result;
+
+  symbol_name_match_type match_type = name_match_type_from_name (name);
+  lookup_name_info lookup_name (name, match_type);
+
+  symbol_name_matcher_ftype *match_name
+    = ada_get_symbol_name_matcher (lookup_name);
+
+  for (objfile *objfile : current_program_space->objfiles ())
+    {
+      for (minimal_symbol *msymbol : objfile->msymbols ())
+	{
+	  if (match_name (MSYMBOL_LINKAGE_NAME (msymbol), lookup_name, NULL)
+	      && MSYMBOL_TYPE (msymbol) != mst_solib_trampoline)
+	    result.push_back ({msymbol, objfile});
+	}
+    }
+
+  return result;
+}
+
 /* For all subprograms that statically enclose the subprogram of the
    selected frame, add symbols matching identifier NAME in DOMAIN
    and their blocks to the list of data in OBSTACKP, as for
@@ -12437,8 +12468,6 @@ static void
 create_excep_cond_exprs (struct ada_catchpoint *c,
                          enum ada_exception_catchpoint_kind ex)
 {
-  struct bp_location *bl;
-
   /* Nothing to do if there's no specific exception to catch.  */
   if (c->excep_string.empty ())
     return;
@@ -12447,28 +12476,45 @@ create_excep_cond_exprs (struct ada_catchpoint *c,
   if (c->loc == NULL)
     return;
 
-  /* Compute the condition expression in text form, from the specific
-     expection we want to catch.  */
-  std::string cond_string
-    = ada_exception_catchpoint_cond_string (c->excep_string.c_str (), ex);
+  /* We have to compute the expression once for each program space,
+     because the expression may hold the addresses of multiple symbols
+     in some cases.  */
+  std::multimap<program_space *, struct bp_location *> loc_map;
+  for (struct bp_location *bl = c->loc; bl != NULL; bl = bl->next)
+    loc_map.emplace (bl->pspace, bl);
+
+  scoped_restore_current_program_space save_pspace;
 
-  /* Iterate over all the catchpoint's locations, and parse an
-     expression for each.  */
-  for (bl = c->loc; bl != NULL; bl = bl->next)
+  std::string cond_string;
+  program_space *last_ps = nullptr;
+  for (auto iter : loc_map)
     {
       struct ada_catchpoint_location *ada_loc
-	= (struct ada_catchpoint_location *) bl;
+	= (struct ada_catchpoint_location *) iter.second;
+
+      if (ada_loc->pspace != last_ps)
+	{
+	  last_ps = ada_loc->pspace;
+	  set_current_program_space (last_ps);
+
+	  /* Compute the condition expression in text form, from the
+	     specific expection we want to catch.  */
+	  cond_string
+	    = ada_exception_catchpoint_cond_string (c->excep_string.c_str (),
+						    ex);
+	}
+
       expression_up exp;
 
-      if (!bl->shlib_disabled)
+      if (!ada_loc->shlib_disabled)
 	{
 	  const char *s;
 
 	  s = cond_string.c_str ();
 	  try
 	    {
-	      exp = parse_exp_1 (&s, bl->address,
-				 block_for_pc (bl->address),
+	      exp = parse_exp_1 (&s, ada_loc->address,
+				 block_for_pc (ada_loc->address),
 				 0);
 	    }
 	  catch (const gdb_exception_error &e)
@@ -13130,18 +13176,18 @@ ada_exception_catchpoint_cond_string (const char *excep_string,
                                       enum ada_exception_catchpoint_kind ex)
 {
   int i;
-  bool is_standard_exc = false;
   std::string result;
+  const char *name;
 
   if (ex == ada_catch_handlers)
     {
       /* For exception handlers catchpoints, the condition string does
          not use the same parameter as for the other exceptions.  */
-      result = ("long_integer (GNAT_GCC_exception_Access"
-		"(gcc_exception).all.occurrence.id)");
+      name = ("long_integer (GNAT_GCC_exception_Access"
+	      "(gcc_exception).all.occurrence.id)");
     }
   else
-    result = "long_integer (e)";
+    name = "long_integer (e)";
 
   /* The standard exceptions are a special case.  They are defined in
      runtime units that have been compiled without debugging info; if
@@ -13160,23 +13206,35 @@ ada_exception_catchpoint_cond_string (const char *excep_string,
      If an exception named contraint_error is defined in another package of
      the inferior program, then the only way to specify this exception as a
      breakpoint condition is to use its fully-qualified named:
-     e.g. my_package.constraint_error.  */
+     e.g. my_package.constraint_error.
+
+     Furthermore, in some situations a standard exception's symbol may
+     be present in more than one objfile, because the compiler may
+     choose to emit copy relocations for them.  So, we have to compare
+     against all the possible addresses.  */
 
+  /* Storage for a rewritten symbol name.  */
+  std::string std_name;
   for (i = 0; i < sizeof (standard_exc) / sizeof (char *); i++)
     {
       if (strcmp (standard_exc [i], excep_string) == 0)
 	{
-	  is_standard_exc = true;
+	  std_name = std::string ("standard.") + excep_string;
+	  excep_string = std_name.c_str ();
 	  break;
 	}
     }
 
-  result += " = ";
-
-  if (is_standard_exc)
-    string_appendf (result, "long_integer (&standard.%s)", excep_string);
-  else
-    string_appendf (result, "long_integer (&%s)", excep_string);
+  excep_string = ada_encode (excep_string);
+  std::vector<struct bound_minimal_symbol> symbols
+    = ada_lookup_simple_minsyms (excep_string);
+  for (const struct bound_minimal_symbol &msym : symbols)
+    {
+      if (!result.empty ())
+	result += " or ";
+      string_appendf (result, "%s = %s", name,
+		      pulongest (BMSYMBOL_VALUE_ADDRESS (msym)));
+    }
 
   return result;
 }