Eliminate most remaining cleanups under gdb/guile/

The main complication with the Guile code is that we have two types of
exceptions to consider.  GDB/C++ exceptions, and Guile/SJLJ
exceptions.  Code that is facing the Guile interpreter must not throw
GDB exceptions, instead Scheme exceptions must be thrown.  Also,
because Guile exceptions are SJLJ based, Guile-facing code must not
use local objects with dtors, unless wrapped in a scope with a
TRY/CATCH, because the dtors won't otherwise be run when a Guile
exceptions is thrown.

This commit adds a new gdbscm_wrap wrapper function than encapsulates
a pattern I noticed in many of the functions using
GDBSCM_HANDLE_GDB_EXCEPTION_WITH_CLEANUPS.  The wrapper is written
such that you can pass either a lambda to it, or a function plus a
variable number of forwarded args.  I used a lambda when its body
would be reasonably short, and a separate function in the larger
cases.

This also convers a few functions that were using
GDBSCM_HANDLE_GDB_EXCEPTION to use gdbscm_wrap too because they
followed a similar pattern.

A few cases of make_cleanup calls are replaced with explicit xfree
calls.  The make_cleanup/do_cleanups calls in those cases are
pointless, because do_cleanups won't be called when a Scheme exception
is thrown.

We also have a couple cases of Guile-facing code using RAII-type
objects to manage memory, but those are incorrect, exactly because
their dtor won't be called if a Guile exception is thrown.

gdb/ChangeLog:
2018-07-18  Pedro Alves  <palves@redhat.com>

	* guile/guile-internal.h: Add comment about mixing GDB and Scheme
	exceptions.
	(GDBSCM_HANDLE_GDB_EXCEPTION_WITH_CLEANUPS): Delete.
	(gdbscm_wrap): New.
	* guile/scm-frame.c (gdbscm_frame_read_register): Use xfree
	directly instead of a cleanup.
	* guile/scm-math.c (vlscm_unop_gdbthrow): New, factored out from ...
	(vlscm_unop): ... this.  Reimplement using gdbscm_wrap.
	(vlscm_binop_gdbthrow): New, factored out from ...
	(vlscm_binop): ... this.  Reimplement using gdbscm_wrap.
	(vlscm_rich_compare): Use gdbscm_wrap.
	* guile/scm-symbol.c (gdbscm_lookup_symbol): Use xfree directly
	instead of a cleanup.
	(gdbscm_lookup_global_symbol): Use xfree directly instead of a
	cleanup.
	* guile/scm-type.c (gdbscm_type_field, gdbscm_type_has_field_p):
	Use xfree directly instead of a cleanup.
	* guile/scm-value.c (gdbscm_make_value, gdbscm_make_lazy_value):
	Adjust to use gdbscm_wrap and scoped_value_mark.
	(gdbscm_value_optimized_out_p): Adjust to use gdbscm_wrap.
	(gdbscm_value_address, gdbscm_value_dereference)
	(gdbscm_value_referenced_value): Adjust to use gdbscm_wrap and
	scoped_value_mark.
	(gdbscm_value_dynamic_type): Use scoped_value_mark.
	(vlscm_do_cast, gdbscm_value_field): Adjust to use gdbscm_wrap and
	scoped_value_mark.
	(gdbscm_value_subscript, gdbscm_value_call): Adjust to use
	gdbscm_wrap and scoped_value_mark.
	(gdbscm_value_to_string): Use xfree directly instead of a
	cleanup.  Move 'buffer' unique_ptr to TRY scope.
	(gdbscm_value_to_lazy_string): Use xfree directly instead of a
	cleanup.  Move 'buffer' unique_ptr to TRY scope.  Use
	scoped_value_mark.
	(gdbscm_value_fetch_lazy_x): Use gdbscm_wrap.
	(gdbscm_parse_and_eval): Adjust to use gdbscm_wrap and
	scoped_value_mark.
	(gdbscm_history_ref, gdbscm_history_append_x): Adjust to use
	gdbscm_wrap.

1 files changed, 6 insertions, 11 deletions

diff --git a/gdb/guile/scm-symbol.c b/gdb/guile/scm-symbol.c
index 8802706..8495ca5 100644
--- a/gdb/guile/scm-symbol.c
+++ b/gdb/guile/scm-symbol.c
@@ -582,16 +582,12 @@ gdbscm_lookup_symbol (SCM name_scm, SCM rest)
   int block_arg_pos = -1, domain_arg_pos = -1;
   struct field_of_this_result is_a_field_of_this;
   struct symbol *symbol = NULL;
-  struct cleanup *cleanups;
-  struct gdb_exception except = exception_none;
 
   gdbscm_parse_function_args (FUNC_NAME, SCM_ARG1, keywords, "s#Oi",
 			      name_scm, &name, rest,
 			      &block_arg_pos, &block_scm,
 			      &domain_arg_pos, &domain);
 
-  cleanups = make_cleanup (xfree, name);
-
   if (block_arg_pos >= 0)
     {
       SCM except_scm;
@@ -600,7 +596,7 @@ gdbscm_lookup_symbol (SCM name_scm, SCM rest)
 				  &except_scm);
       if (block == NULL)
 	{
-	  do_cleanups (cleanups);
+	  xfree (name);
 	  gdbscm_throw (except_scm);
 	}
     }
@@ -615,11 +611,13 @@ gdbscm_lookup_symbol (SCM name_scm, SCM rest)
 	}
       CATCH (except, RETURN_MASK_ALL)
 	{
-	  GDBSCM_HANDLE_GDB_EXCEPTION_WITH_CLEANUPS (except, cleanups);
+	  xfree (name);
+	  GDBSCM_HANDLE_GDB_EXCEPTION (except);
 	}
       END_CATCH
     }
 
+  struct gdb_exception except = exception_none;
   TRY
     {
       symbol = lookup_symbol (name, block, (domain_enum) domain,
@@ -631,7 +629,7 @@ gdbscm_lookup_symbol (SCM name_scm, SCM rest)
     }
   END_CATCH
 
-  do_cleanups (cleanups);
+  xfree (name);
   GDBSCM_HANDLE_GDB_EXCEPTION (except);
 
   if (symbol == NULL)
@@ -652,15 +650,12 @@ gdbscm_lookup_global_symbol (SCM name_scm, SCM rest)
   int domain_arg_pos = -1;
   int domain = VAR_DOMAIN;
   struct symbol *symbol = NULL;
-  struct cleanup *cleanups;
   struct gdb_exception except = exception_none;
 
   gdbscm_parse_function_args (FUNC_NAME, SCM_ARG1, keywords, "s#i",
 			      name_scm, &name, rest,
 			      &domain_arg_pos, &domain);
 
-  cleanups = make_cleanup (xfree, name);
-
   TRY
     {
       symbol = lookup_global_symbol (name, NULL, (domain_enum) domain).symbol;
@@ -671,7 +666,7 @@ gdbscm_lookup_global_symbol (SCM name_scm, SCM rest)
     }
   END_CATCH
 
-  do_cleanups (cleanups);
+  xfree (name);
   GDBSCM_HANDLE_GDB_EXCEPTION (except);
 
   if (symbol == NULL)