diff --git a/src/libCom/calc/postfix.c b/src/libCom/calc/postfix.c
index c71c615d0..8ff596d3d 100644
--- a/src/libCom/calc/postfix.c
+++ b/src/libCom/calc/postfix.c
@@ -291,7 +291,7 @@ long epicsShareAPI postfix(const char *pin,char *ppostfix,short *perror)
         strcpy(infix,pin);
 	/* convert infix expression to upper case */
 	for (pc=pinfix; *pc; pc++) {
-		if (islower(*pc)) *pc = toupper(*pc);
+		if (islower((int)*pc)) *pc = toupper((int)*pc);
 	}
 
 	/* place the expression elements into postfix */
diff --git a/src/libCom/calc/sCalcPerform.c b/src/libCom/calc/sCalcPerform.c
index 1903c5745..2c5bc1eda 100644
--- a/src/libCom/calc/sCalcPerform.c
+++ b/src/libCom/calc/sCalcPerform.c
@@ -303,7 +303,7 @@ epicsShareFunc long epicsShareAPI
 			case FETCH:
 				++pd;
 				++post;
-				*pd = (*post < numArgs) ? parg[*post] : 0;
+				*pd = (*post < numArgs) ? parg[(int)*post] : 0;
 				break;
 
 			case STORE:
@@ -646,7 +646,7 @@ printf(") \n");
 				INC(ps);
 				++post;
 				ps->s = NULL;
-				ps->d = (*post < numArgs) ? parg[*post] : 0;
+				ps->d = (*post < numArgs) ? parg[(int)*post] : 0;
 				break;
 
 			case SFETCH:
@@ -654,8 +654,8 @@ printf(") \n");
 				++post;
 				if (*post < numSArgs) {
 					/* fetch from string variable */
-					ps->s = calloc(strlen(psarg[*post])+1, 1);
-					strcpy(ps->s, psarg[*post]);
+					ps->s = calloc(strlen(psarg[(int)*post])+1, 1);
+					strcpy(ps->s, psarg[(int)*post]);
 				} else {
 					/* fetch from variable that caller did not supply */
 					ps->s = calloc(1, 1);
diff --git a/src/libCom/macLib/macUtil.c b/src/libCom/macLib/macUtil.c
index 4aa8c43ab..71c7d9bfc 100644
--- a/src/libCom/macLib/macUtil.c
+++ b/src/libCom/macLib/macUtil.c
@@ -92,7 +92,7 @@ epicsShareAPI macParseDefns(
 
 	switch ( state ) {
 	  case preName:
-	    if ( !quote && !escape && ( isspace( *c ) || *c == ',' ) ) break;
+	    if ( !quote && !escape && ( isspace( (int) *c ) || *c == ',' ) ) break;
 	    ptr[num] = c;
 	    state = inName;
 	    /* fall through (may be empty name) */
@@ -100,7 +100,7 @@ epicsShareAPI macParseDefns(
 	  case inName:
 	    if ( quote || escape || ( *c != '=' && *c != ',' ) ) break;
 	    end[num] = c;
-	    while ( end[num] > ptr[num] && isspace( *( end[num] - 1 ) ) )
+	    while ( end[num] > ptr[num] && isspace( (int) *( end[num] - 1 ) ) )
 		end[num]--;
 	    num++;
 	    del[num] = FALSE;
@@ -110,7 +110,7 @@ epicsShareAPI macParseDefns(
 	    /* fall through (','; will delete) */
 
 	  case preValue:
-	    if ( !quote && !escape && isspace( *c ) ) break;
+	    if ( !quote && !escape && isspace( (int) *c ) ) break;
 	    ptr[num] = c;
 	    state = inValue;
 	    /* fall through (may be empty value) */
@@ -118,7 +118,7 @@ epicsShareAPI macParseDefns(
 	  case inValue:
 	    if ( quote || escape || *c != ',' ) break;
 	    end[num] = c;
-	    while ( end[num] > ptr[num] && isspace( *( end[num] - 1 ) ) )
+	    while ( end[num] > ptr[num] && isspace( (int) *( end[num] - 1 ) ) )
 		end[num]--;
 	    num++;
 	    del[num] = FALSE;
@@ -138,7 +138,7 @@ epicsShareAPI macParseDefns(
 	break;
       case inName:
 	end[num] = c;
-	while ( end[num] > ptr[num] && isspace( *( end[num] - 1 ) ) )
+	while ( end[num] > ptr[num] && isspace( (int) *( end[num] - 1 ) ) )
 	    end[num]--;
 	num++;
 	del[num] = TRUE;
@@ -146,7 +146,7 @@ epicsShareAPI macParseDefns(
 	ptr[num] = c;
       case inValue:
 	end[num] = c;
-	while ( end[num] > ptr[num] && isspace( *( end[num] - 1 ) ) )
+	while ( end[num] > ptr[num] && isspace( (int) *( end[num] - 1 ) ) )
 	    end[num]--;
 	num++;
 	del[num] = FALSE;
diff --git a/src/libCom/misc/epicsString.c b/src/libCom/misc/epicsString.c
index d49704ddf..23b91d3cd 100644
--- a/src/libCom/misc/epicsString.c
+++ b/src/libCom/misc/epicsString.c
@@ -63,7 +63,7 @@ int dbTranslateEscape(char *to, const char *from)
 
                 pfrom++; /*skip the x*/
 		for(i=0; i<2; i++) {
-		    if(!isxdigit(*pfrom)) break;
+		    if(!isxdigit((int)*pfrom)) break;
 		    strval[i] = *pfrom++;
 		}
 		sscanf(strval,"%x",&ival);