From 0f027df00c6ede01458e70206193721bad6cbf2a Mon Sep 17 00:00:00 2001
From: vsc <vsc@b08c6af1-5177-4d33-ba66-4b1c6b8b522a>
Date: Tue, 11 Jun 2002 05:43:01 +0000
Subject: [PATCH] fix backtrackable C-interface (patch from Christophe
 Billard).

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@526 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
---
 C/absmi.c            |  4 ++--
 C/c_interface.c      | 25 +++++++++++--------------
 H/Yapproto.h         |  4 ++--
 changes4.3.html      |  2 ++
 library/system/sys.c |  4 +++-
 5 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/C/absmi.c b/C/absmi.c
index f01b2b1a6..493782721 100644
--- a/C/absmi.c
+++ b/C/absmi.c
@@ -5760,7 +5760,7 @@ absmi(int inp)
 	saveregs();
 	save_machine_regs();
 
-	SREG = (CELL *) YapExecute(p);
+	SREG = (CELL *) YapExecute(p, (CPredicate)(p->TrueCodeOfPred));
       }
 
       restore_machine_regs();
@@ -5888,7 +5888,7 @@ absmi(int inp)
       ASP = YENV;
       saveregs();
       save_machine_regs();
-      SREG = (CELL *) YapExecute(PREG->u.lds.p);
+      SREG = (CELL *) YapExecute(PREG->u.lds.p, (CPredicate)(PREG->u.lds.d));
       restore_machine_regs();
       setregs();
       if (!SREG) {
diff --git a/C/c_interface.c b/C/c_interface.c
index d4586aa3a..1f2d357fb 100644
--- a/C/c_interface.c
+++ b/C/c_interface.c
@@ -74,7 +74,6 @@ X_API Int     STD_PROTO(Yapcut_fail,(void));
 X_API Int     STD_PROTO(Yapcut_succeed,(void));
 X_API Int     STD_PROTO(YapUnify,(Term,Term));
 X_API Int     STD_PROTO(YapUnify,(Term,Term));
-      Int     STD_PROTO(YapExecute,(PredEntry *));
 X_API int     STD_PROTO(YapReset,(void));
 X_API Int     STD_PROTO(YapInit,(yap_init_args *));
 X_API Int     STD_PROTO(YapFastInit,(char *));
@@ -482,37 +481,36 @@ typedef Int (*CPredicate7)(long,long,long,long,long,long,long);
 typedef Int (*CPredicate8)(long,long,long,long,long,long,long,long);
 
 Int
-YapExecute(PredEntry *pe)
+YapExecute(PredEntry *pe, CPredicate exec_code)
 {
   if (pe->PredFlags & CArgsPredFlag) {
-    CODEADDR code = pe->TrueCodeOfPred;
     switch (pe->ArityOfPE) {
     case 0:
       {
-	CPredicate code0 = (CPredicate)code;
+	CPredicate code0 = exec_code;
 	return ((code0)());
       }
     case 1:
       {
-	CPredicate1 code1 = (CPredicate1)code;
+	CPredicate1 code1 = (CPredicate1)exec_code;
 	return ((code1)(YapInitSlot(Deref(ARG1))));
       }
     case 2:
       {
-	CPredicate2 code2 = (CPredicate2)code;
+	CPredicate2 code2 = (CPredicate2)exec_code;
 	return ((code2)(YapInitSlot(Deref(ARG1)),
 			YapInitSlot(Deref(ARG2))));
       }
     case 3:
       {
-	CPredicate3 code3 = (CPredicate3)code;
+	CPredicate3 code3 = (CPredicate3)exec_code;
 	return ((code3)(YapInitSlot(Deref(ARG1)),
 			YapInitSlot(Deref(ARG2)),
 			YapInitSlot(Deref(ARG3))));
       }
     case 4:
       {
-	CPredicate4 code4 = (CPredicate4)code;
+	CPredicate4 code4 = (CPredicate4)exec_code;
 	return ((code4)(YapInitSlot(Deref(ARG1)),
 			YapInitSlot(Deref(ARG2)),
 			YapInitSlot(Deref(ARG3)),
@@ -520,7 +518,7 @@ YapExecute(PredEntry *pe)
       }
     case 5:
       {
-	CPredicate5 code5 = (CPredicate5)code;
+	CPredicate5 code5 = (CPredicate5)exec_code;
 	return ((code5)(YapInitSlot(Deref(ARG1)),
 			YapInitSlot(Deref(ARG2)),
 			YapInitSlot(Deref(ARG3)),
@@ -528,7 +526,7 @@ YapExecute(PredEntry *pe)
       }
     case 6:
       {
-	CPredicate6 code6 = (CPredicate6)code;
+	CPredicate6 code6 = (CPredicate6)exec_code;
 	return ((code6)(YapInitSlot(Deref(ARG1)),
 			YapInitSlot(Deref(ARG2)),
 			YapInitSlot(Deref(ARG3)),
@@ -538,7 +536,7 @@ YapExecute(PredEntry *pe)
       }
     case 7:
       {
-	CPredicate7 code7 = (CPredicate7)code;
+	CPredicate7 code7 = (CPredicate7)exec_code;
 	return ((code7)(YapInitSlot(Deref(ARG1)),
 			YapInitSlot(Deref(ARG2)),
 			YapInitSlot(Deref(ARG3)),
@@ -549,7 +547,7 @@ YapExecute(PredEntry *pe)
       }
     case 8:
       {
-	CPredicate8 code8 = (CPredicate8)code;
+	CPredicate8 code8 = (CPredicate8)exec_code;
 	return ((code8)(YapInitSlot(Deref(ARG1)),
 			YapInitSlot(Deref(ARG2)),
 			YapInitSlot(Deref(ARG3)),
@@ -563,8 +561,7 @@ YapExecute(PredEntry *pe)
       return(FALSE);
     }
   } else {
-    CPredicate code = (CPredicate)(pe->TrueCodeOfPred);
-    return((code)());
+    return((exec_code)());
   }
 }
 
diff --git a/H/Yapproto.h b/H/Yapproto.h
index 1934d2981..b807c9a23 100644
--- a/H/Yapproto.h
+++ b/H/Yapproto.h
@@ -10,7 +10,7 @@
 * File:		Yap.proto						 *
 * mods:									 *
 * comments:	Function declarations for YAP				 *
-* version:      $Id: Yapproto.h,v 1.20 2002-06-05 03:59:50 vsc Exp $	 *
+* version:      $Id: Yapproto.h,v 1.21 2002-06-11 05:43:01 vsc Exp $	 *
 *************************************************************************/
 
 /* prototype file for Yap */
@@ -104,7 +104,7 @@ void   STD_PROTO(InitBBPreds,(void));
 void   STD_PROTO(InitBigNums,(void));
 
 /* c_interface.c */
-Int    STD_PROTO(YapExecute,(struct pred_entry *));
+Int    STD_PROTO(YapExecute,(struct pred_entry *, CPredicate));
 
 /* cdmgr.c */
 void	STD_PROTO(mark_as_fast,(Term));
diff --git a/changes4.3.html b/changes4.3.html
index 53f98ba45..df7a645a7 100644
--- a/changes4.3.html
+++ b/changes4.3.html
@@ -16,6 +16,8 @@
 
 <h2>Yap-4.3.23:</h2>
 <ul>
+	<li>FIXED: backtrackable C-predicates (thanks to Christophe
+	Billard for sending the file).</li>
 	<li>FIXED: new options for file_property (Nicos).</li>
 	<li>FIXED: check unification result in file_property (Nicos).</li>
 	<li>FIXED: yap_flag(fileerrors) (Nicos).</li>
diff --git a/library/system/sys.c b/library/system/sys.c
index f1b75f70f..a543e97ba 100644
--- a/library/system/sys.c
+++ b/library/system/sys.c
@@ -276,9 +276,11 @@ file_property(void)
 #if HAVE_READLINK
     {
       char tmp[256];
-      if (readlink(fd,tmp,256) == -1) {
+      int n;
+      if ((n = readlink(fd,tmp,256)) == -1) {
 	return(unify(ARG7, MkIntTerm(errno)));
       }
+      tmp[n] = '\0';
       if(!unify(ARG6,MkAtomTerm(LookupAtom(tmp)))) {
 	return(FALSE);
       }