compatibility: replace iscntrl with own ISCNTRL macro

It is unspecified if the C locale iscntrl is compatible with ASCII or not.

Noticed when testing on OpenBSD 3.8 which uses extended ASCII and also uses the
C1 range for control-characters.  This breaks support with UTF-8.

Reference:
https://en.wikipedia.org/wiki/C0_and_C1_control_codes#C1_control_codes_for_general_use
C1 table.

Force an own definition of an ASCII-compatible control-character range since
sfeed expects input to be UTF-8 (or converted from iconv) and so output to be
UTF-8 aswell.

4 files changed, 7 insertions, 4 deletions

diff --git a/sfeed.c b/sfeed.c
index 9b3fd8f..fc1249a 100644
--- a/sfeed.c
+++ b/sfeed.c
@@ -326,7 +326,7 @@ string_print_encoded(String *s)
 		case '\t': putchar('\\'); putchar('t'); break;
 		default:
 			/* ignore control chars */
-			if (!iscntrl((unsigned char)*p))
+			if (!ISCNTRL((unsigned char)*p))
 				putchar(*p);
 			break;
 		}
@@ -343,7 +343,7 @@ printtrimmed(const char *s)
 	for (; *p && p != e; p++) {
 		if (isspace((unsigned char)*p))
 			putchar(' '); /* any whitespace to space */
-		else if (!iscntrl((unsigned char)*p))
+		else if (!ISCNTRL((unsigned char)*p))
 			/* ignore other control chars */
 			putchar(*p);
 	}
diff --git a/sfeed_opml_import.c b/sfeed_opml_import.c
index 6c0bd0e..9a13e36 100644
--- a/sfeed_opml_import.c
+++ b/sfeed_opml_import.c
@@ -12,7 +12,7 @@ static void
 printsafe(const char *s)
 {
 	for (; *s; s++) {
-		if (iscntrl((unsigned char)*s))
+		if (ISCNTRL((unsigned char)*s))
 			continue;
 		else if (*s == '\\')
 			fputs("\\\\", stdout);
diff --git a/sfeed_web.c b/sfeed_web.c
index 704afe8..dfff0a3 100644
--- a/sfeed_web.c
+++ b/sfeed_web.c
@@ -16,7 +16,7 @@ static void
 printvalue(const char *s)
 {
 	for (; *s; s++)
-		if (!iscntrl((unsigned char)*s))
+		if (!ISCNTRL((unsigned char)*s))
 			putchar(*s);
 }
 
diff --git a/util.h b/util.h
index 7923cdc..c68cef4 100644
--- a/util.h
+++ b/util.h
@@ -8,6 +8,9 @@
 #define unveil(p1,p2) 0
 #endif
 
+/* control-character in the ASCII range 0-127: compatible with UTF-8 */
+#define ISCNTRL(c) ((c) < ' ' || (c) == 0x7f)
+
 #undef strcasestr
 char *strcasestr(const char *, const char *);
 #undef strlcat