* libtiff/tif_fax3.c, libtiff/tif_lzw.c, libtiff/tif_predict.c:

add explicit masking with 0xff before casting
to unsigned char (make icc -check=conversions happy)

* libtiff/tif_predict.c: operate on unsigned datatypes when
computing/applying differences to avoid undefined behaviour of
signed types (C standard compliance)

4 files changed, 59 insertions, 39 deletions

diff --git a/ChangeLog b/ChangeLog
index 49207793..aee767cb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2015-08-30  Even Rouault <even.rouault at spatialys.com>
+
+	* libtiff/tif_fax3.c, libtiff/tif_lzw.c, libtiff/tif_predict.c:
+	add explicit masking with 0xff before casting
+	to unsigned char (make icc -check=conversions happy)
+
+	* libtiff/tif_predict.c: operate on unsigned datatypes when
+	computing/applying differences to avoid undefined behaviour of
+	signed types (C standard compliance)
+
 2015-08-30  Bob Friesenhahn  <bfriesen@simple.dallas.tx.us>
 
 	* configure.ac: libtiff 4.0.5 released.
diff --git a/libtiff/tif_fax3.c b/libtiff/tif_fax3.c
index 2b2dccd0..bbe72555 100644
--- a/libtiff/tif_fax3.c
+++ b/libtiff/tif_fax3.c
@@ -1,4 +1,4 @@
-/* $Id: tif_fax3.c,v 1.74 2012-06-21 02:01:31 fwarmerdam Exp $ */
+/* $Id: tif_fax3.c,v 1.75 2015-08-30 20:49:55 erouault Exp $ */
 
 /*
  * Copyright (c) 1990-1997 Sam Leffler
@@ -442,8 +442,9 @@ _TIFFFax3fillruns(unsigned char* buf, uint32* runs, uint32* erun, uint32 lastx)
 			FILL(n, cp);
 			run &= 7;
 		    }
+                    /* Explicit 0xff masking to make icc -check=conversions happy */
 		    if (run)
-			cp[0] |= 0xff00 >> run;
+			cp[0] = (unsigned char)((cp[0] | (0xff00 >> run))&0xff);
 		} else
 		    cp[0] |= _fillmasks[run]>>bx;
 		x += runs[1];
diff --git a/libtiff/tif_lzw.c b/libtiff/tif_lzw.c
index 58345f0a..ab04bbaa 100644
--- a/libtiff/tif_lzw.c
+++ b/libtiff/tif_lzw.c
@@ -1,4 +1,4 @@
-/* $Id: tif_lzw.c,v 1.47 2015-06-13 05:03:50 faxguy Exp $ */
+/* $Id: tif_lzw.c,v 1.48 2015-08-30 20:49:55 erouault Exp $ */
 
 /*
  * Copyright (c) 1988-1997 Sam Leffler
@@ -836,13 +836,15 @@ LZWPreEncode(TIFF* tif, uint16 s)
 	} else							\
 		rat = (incount<<8) / outcount;			\
 }
+
+/* Explicit 0xff masking to make icc -check=conversions happy */
 #define	PutNextCode(op, c) {					\
 	nextdata = (nextdata << nbits) | c;			\
 	nextbits += nbits;					\
-	*op++ = (unsigned char)(nextdata >> (nextbits-8));		\
+	*op++ = (unsigned char)((nextdata >> (nextbits-8))&0xff);		\
 	nextbits -= 8;						\
 	if (nextbits >= 8) {					\
-		*op++ = (unsigned char)(nextdata >> (nextbits-8));	\
+		*op++ = (unsigned char)((nextdata >> (nextbits-8))&0xff);	\
 		nextbits -= 8;					\
 	}							\
 	outcount += nbits;					\
@@ -1048,8 +1050,9 @@ LZWPostEncode(TIFF* tif)
 		sp->enc_oldcode = (hcode_t) -1;
 	}
 	PutNextCode(op, CODE_EOI);
+        /* Explicit 0xff masking to make icc -check=conversions happy */
 	if (nextbits > 0) 
-		*op++ = (unsigned char)(nextdata << (8-nextbits));
+		*op++ = (unsigned char)((nextdata << (8-nextbits))&0xff);
 	tif->tif_rawcc = (tmsize_t)(op - tif->tif_rawdata);
 	return (1);
 }
diff --git a/libtiff/tif_predict.c b/libtiff/tif_predict.c
index f93c6645..117c6062 100644
--- a/libtiff/tif_predict.c
+++ b/libtiff/tif_predict.c
@@ -1,4 +1,4 @@
-/* $Id: tif_predict.c,v 1.32 2010-03-10 18:56:49 bfriesen Exp $ */
+/* $Id: tif_predict.c,v 1.33 2015-08-30 20:49:55 erouault Exp $ */
 
 /*
  * Copyright (c) 1988-1997 Sam Leffler
@@ -239,12 +239,18 @@ PredictorSetupEncode(TIFF* tif)
     case 0:  ;			\
     }
 
+/* Remarks related to C standard compliance in all below functions : */
+/* - to avoid any undefined behaviour, we only operate on unsigned types */
+/*   since the behaviour of "overflows" is defined (wrap over) */
+/* - when storing into the byte stream, we explicitly mask with 0xff so */
+/*   as to make icc -check=conversions happy (not necessary by the standard) */
+
 static void
 horAcc8(TIFF* tif, uint8* cp0, tmsize_t cc)
 {
 	tmsize_t stride = PredictorState(tif)->stride;
 
-	char* cp = (char*) cp0;
+	unsigned char* cp = (unsigned char*) cp0;
 	assert((cc%stride)==0);
 	if (cc > stride) {
 		/*
@@ -257,9 +263,9 @@ horAcc8(TIFF* tif, uint8* cp0, tmsize_t cc)
 			cc -= 3;
 			cp += 3;
 			while (cc>0) {
-				cp[0] = (char) (cr += cp[0]);
-				cp[1] = (char) (cg += cp[1]);
-				cp[2] = (char) (cb += cp[2]);
+				cp[0] = (unsigned char) ((cr += cp[0]) & 0xff);
+				cp[1] = (unsigned char) ((cg += cp[1]) & 0xff);
+				cp[2] = (unsigned char) ((cb += cp[2]) & 0xff);
 				cc -= 3;
 				cp += 3;
 			}
@@ -271,10 +277,10 @@ horAcc8(TIFF* tif, uint8* cp0, tmsize_t cc)
 			cc -= 4;
 			cp += 4;
 			while (cc>0) {
-				cp[0] = (char) (cr += cp[0]);
-				cp[1] = (char) (cg += cp[1]);
-				cp[2] = (char) (cb += cp[2]);
-				cp[3] = (char) (ca += cp[3]);
+				cp[0] = (unsigned char) ((cr += cp[0]) & 0xff);
+				cp[1] = (unsigned char) ((cg += cp[1]) & 0xff);
+				cp[2] = (unsigned char) ((cb += cp[2]) & 0xff);
+				cp[3] = (unsigned char) ((ca += cp[3]) & 0xff);
 				cc -= 4;
 				cp += 4;
 			}
@@ -282,7 +288,7 @@ horAcc8(TIFF* tif, uint8* cp0, tmsize_t cc)
 			cc -= stride;
 			do {
 				REPEAT4(stride, cp[stride] =
-					(char) (cp[stride] + *cp); cp++)
+					(unsigned char) ((cp[stride] + *cp) & 0xff); cp++)
 				cc -= stride;
 			} while (cc>0);
 		}
@@ -302,7 +308,7 @@ swabHorAcc16(TIFF* tif, uint8* cp0, tmsize_t cc)
 		TIFFSwabArrayOfShort(wp, wc);
 		wc -= stride;
 		do {
-			REPEAT4(stride, wp[stride] += wp[0]; wp++)
+			REPEAT4(stride, wp[stride] = (uint16)(((unsigned int)wp[stride] + (unsigned int)wp[0]) & 0xffff); wp++)
 			wc -= stride;
 		} while (wc > 0);
 	}
@@ -320,7 +326,7 @@ horAcc16(TIFF* tif, uint8* cp0, tmsize_t cc)
 	if (wc > stride) {
 		wc -= stride;
 		do {
-			REPEAT4(stride, wp[stride] += wp[0]; wp++)
+			REPEAT4(stride, wp[stride] = (uint16)(((unsigned int)wp[stride] + (unsigned int)wp[0]) & 0xffff); wp++)
 			wc -= stride;
 		} while (wc > 0);
 	}
@@ -456,7 +462,7 @@ horDiff8(TIFF* tif, uint8* cp0, tmsize_t cc)
 {
 	TIFFPredictorState* sp = PredictorState(tif);
 	tmsize_t stride = sp->stride;
-	char* cp = (char*) cp0;
+	unsigned char* cp = (unsigned char*) cp0;
 
 	assert((cc%stride)==0);
 
@@ -466,33 +472,33 @@ horDiff8(TIFF* tif, uint8* cp0, tmsize_t cc)
 		 * Pipeline the most common cases.
 		 */
 		if (stride == 3) {
-			int r1, g1, b1;
-			int r2 = cp[0];
-			int g2 = cp[1];
-			int b2 = cp[2];
+			unsigned int r1, g1, b1;
+			unsigned int r2 = cp[0];
+			unsigned int g2 = cp[1];
+			unsigned  int b2 = cp[2];
 			do {
-				r1 = cp[3]; cp[3] = r1-r2; r2 = r1;
-				g1 = cp[4]; cp[4] = g1-g2; g2 = g1;
-				b1 = cp[5]; cp[5] = b1-b2; b2 = b1;
+				r1 = cp[3]; cp[3] = (unsigned char)((r1-r2)&0xff); r2 = r1;
+				g1 = cp[4]; cp[4] = (unsigned char)((g1-g2)&0xff); g2 = g1;
+				b1 = cp[5]; cp[5] = (unsigned char)((b1-b2)&0xff); b2 = b1;
 				cp += 3;
 			} while ((cc -= 3) > 0);
 		} else if (stride == 4) {
-			int r1, g1, b1, a1;
-			int r2 = cp[0];
-			int g2 = cp[1];
-			int b2 = cp[2];
-			int a2 = cp[3];
+			unsigned int r1, g1, b1, a1;
+			unsigned int r2 = cp[0];
+			unsigned int g2 = cp[1];
+			unsigned int b2 = cp[2];
+			unsigned int a2 = cp[3];
 			do {
-				r1 = cp[4]; cp[4] = r1-r2; r2 = r1;
-				g1 = cp[5]; cp[5] = g1-g2; g2 = g1;
-				b1 = cp[6]; cp[6] = b1-b2; b2 = b1;
-				a1 = cp[7]; cp[7] = a1-a2; a2 = a1;
+				r1 = cp[4]; cp[4] = (unsigned char)((r1-r2)&0xff); r2 = r1;
+				g1 = cp[5]; cp[5] = (unsigned char)((g1-g2)&0xff); g2 = g1;
+				b1 = cp[6]; cp[6] = (unsigned char)((b1-b2)&0xff); b2 = b1;
+				a1 = cp[7]; cp[7] = (unsigned char)((a1-a2)&0xff); a2 = a1;
 				cp += 4;
 			} while ((cc -= 4) > 0);
 		} else {
 			cp += cc - 1;
 			do {
-				REPEAT4(stride, cp[stride] -= cp[0]; cp--)
+				REPEAT4(stride, cp[stride] = (unsigned char)((cp[stride] - cp[0])&0xff); cp--)
 			} while ((cc -= stride) > 0);
 		}
 	}
@@ -503,7 +509,7 @@ horDiff16(TIFF* tif, uint8* cp0, tmsize_t cc)
 {
 	TIFFPredictorState* sp = PredictorState(tif);
 	tmsize_t stride = sp->stride;
-	int16 *wp = (int16*) cp0;
+	uint16 *wp = (uint16*) cp0;
 	tmsize_t wc = cc/2;
 
 	assert((cc%(2*stride))==0);
@@ -512,7 +518,7 @@ horDiff16(TIFF* tif, uint8* cp0, tmsize_t cc)
 		wc -= stride;
 		wp += wc - 1;
 		do {
-			REPEAT4(stride, wp[stride] -= wp[0]; wp--)
+			REPEAT4(stride, wp[stride] = (uint16)(((unsigned int)wp[stride] - (unsigned int)wp[0]) & 0xffff); wp--)
 			wc -= stride;
 		} while (wc > 0);
 	}
@@ -523,7 +529,7 @@ horDiff32(TIFF* tif, uint8* cp0, tmsize_t cc)
 {
 	TIFFPredictorState* sp = PredictorState(tif);
 	tmsize_t stride = sp->stride;
-	int32 *wp = (int32*) cp0;
+	uint32 *wp = (uint32*) cp0;
 	tmsize_t wc = cc/4;
 
 	assert((cc%(4*stride))==0);