GNU bug report logs - #25289
Simplify calls to setjmp for condition case

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From: Chris Gregory <czipperz <at> gmail.com>
To: 25289 <at> debbugs.gnu.org
Subject: bug#25289: Simplify calls to setjmp for condition case
Date: Wed, 28 Dec 2016 18:32:18 -0600

This patch simplifies calls to setjmp, while keeping the semantics of
setjmp valid (it must be called in an if statement or some loop with
a comparison operator).

This takes the common bodies out of the branches.

-- 
Chris Gregory

diff --git a/src/eval.c b/src/eval.c
index e50e26a..6d50b98 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1084,22 +1084,19 @@ internal_catch (Lisp_Object tag,
 {
   /* This structure is made part of the chain `catchlist'.  */
   struct handler *c = push_handler (tag, CATCHER);
+  Lisp_Object val;
 
-  /* Call FUNC.  */
-  if (! sys_setjmp (c->jmp))
-    {
-      Lisp_Object val = func (arg);
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return val;
-    }
+  // This if statement is not redundant. setjmp must be called in an
+  // if statement.
+  if (sys_setjmp (c->jmp) != 0)
+    /* Throw works by a longjmp that comes right here. */
+    val = handlerlist->val;
   else
-    { /* Throw works by a longjmp that comes right here.  */
-      Lisp_Object val = handlerlist->val;
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return val;
-    }
+    val = func (arg);
+
+  clobbered_eassert (handlerlist == c);
+  handlerlist = handlerlist->next;
+  return val;
 }
 
 /* Unwind the specbind, catch, and handler stacks back to CATCH, and
@@ -1313,20 +1310,24 @@ internal_condition_case (Lisp_Object (*bfun) (void), Lisp_Object handlers,
 			 Lisp_Object (*hfun) (Lisp_Object))
 {
   struct handler *c = push_handler (handlers, CONDITION_CASE);
-  if (sys_setjmp (c->jmp))
+  Lisp_Object val;
+  bool is_recursive;
+
+  // This if statement is not redundant. setjmp must be called in an
+  // if statement.
+  if (sys_setjmp (c->jmp) != 0)
     {
-      Lisp_Object val = handlerlist->val;
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return hfun (val);
+      is_recursive = true;
+      val = handlerlist->val;
     }
   else
     {
-      Lisp_Object val = bfun ();
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return val;
+      is_recursive = false;
+      val = bfun ();
     }
+  clobbered_eassert (handlerlist == c);
+  handlerlist = handlerlist->next;
+  return is_recursive ? hfun (val) : val;
 }
 
 /* Like internal_condition_case but call BFUN with ARG as its argument.  */
@@ -1337,20 +1338,24 @@ internal_condition_case_1 (Lisp_Object (*bfun) (Lisp_Object), Lisp_Object arg,
 			   Lisp_Object (*hfun) (Lisp_Object))
 {
   struct handler *c = push_handler (handlers, CONDITION_CASE);
-  if (sys_setjmp (c->jmp))
+  Lisp_Object val;
+  bool is_recursive;
+
+  // This if statement is not redundant. setjmp must be called in an
+  // if statement.
+  if (sys_setjmp (c->jmp) != 0)
     {
-      Lisp_Object val = handlerlist->val;
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return hfun (val);
+      is_recursive = true;
+      val = handlerlist->val;
     }
   else
     {
-      Lisp_Object val = bfun (arg);
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return val;
+      is_recursive = false;
+      val = bfun (arg);
     }
+  clobbered_eassert (handlerlist == c);
+  handlerlist = handlerlist->next;
+  return is_recursive ? hfun (val) : val;
 }
 
 /* Like internal_condition_case_1 but call BFUN with ARG1 and ARG2 as
@@ -1364,20 +1369,24 @@ internal_condition_case_2 (Lisp_Object (*bfun) (Lisp_Object, Lisp_Object),
 			   Lisp_Object (*hfun) (Lisp_Object))
 {
   struct handler *c = push_handler (handlers, CONDITION_CASE);
-  if (sys_setjmp (c->jmp))
+  Lisp_Object val;
+  bool is_recursive;
+
+  // This if statement is not redundant. setjmp must be called in an
+  // if statement.
+  if (sys_setjmp (c->jmp) != 0)
     {
-      Lisp_Object val = handlerlist->val;
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return hfun (val);
+      is_recursive = true;
+      val = handlerlist->val;
     }
   else
     {
-      Lisp_Object val = bfun (arg1, arg2);
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return val;
+      is_recursive = false;
+      val = bfun (arg1, arg2);
     }
+  clobbered_eassert (handlerlist == c);
+  handlerlist = handlerlist->next;
+  return is_recursive ? hfun (val) : val;
 }
 
 /* Like internal_condition_case but call BFUN with NARGS as first,
@@ -1393,20 +1402,24 @@ internal_condition_case_n (Lisp_Object (*bfun) (ptrdiff_t, Lisp_Object *),
 						Lisp_Object *args))
 {
   struct handler *c = push_handler (handlers, CONDITION_CASE);
-  if (sys_setjmp (c->jmp))
+  Lisp_Object val;
+  bool is_recursive;
+
+  // This if statement is not redundant. setjmp must be called in an
+  // if statement.
+  if (sys_setjmp (c->jmp) != 0)
     {
-      Lisp_Object val = handlerlist->val;
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return hfun (val, nargs, args);
+      is_recursive = true;
+      val = handlerlist->val;
     }
   else
     {
-      Lisp_Object val = bfun (nargs, args);
-      clobbered_eassert (handlerlist == c);
-      handlerlist = handlerlist->next;
-      return val;
+      is_recursive = false;
+      val = bfun (nargs, args);
     }
+  clobbered_eassert (handlerlist == c);
+  handlerlist = handlerlist->next;
+  return is_recursive ? hfun (val, nargs, args) : val;
 }
 
 struct handler *

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