string: strerror_r() implementation

include/string.h

@@ -115,6 +115,10 @@ extern size_t strcspn(const char *str1, const char *str2);
 extern char *strerror(int errnum);
 
 
+/* Thread-safe strerror. */
+extern int strerror_r(int errnum, char *buf, size_t buflen);
+
+
 /* Computes the length of the string str up to but not including the terminating null character. */
 extern size_t strlen(const char *str);
 

string/strerror.c

@@ -16,6 +16,7 @@
 #include <stdlib.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <string.h>
 #include <errno.h>
 
 
@@ -44,7 +45,6 @@ static const errinfo_t gaitab[] = {
 // static assert: 16-bit offset
 static const char assert_errnames_size[-(sizeof(errnames) > 0xFFFF)] __attribute__((unused));
 static const char assert_gainames_size[-(sizeof(gainames) > 0xFFFF)] __attribute__((unused));
-static char err_unknownMsg[32]; /* FIXME: Make thread safe? IMHO overkill */
 
 
 static int err_cmp(const void *key, const void *elem)
@@ -56,7 +56,7 @@ static int err_cmp(const void *key, const void *elem)
 }
 
 
-static inline const char *strerror_(const errinfo_t *tab, size_t tabsz, const char *names, int errnum)
+static inline const char *strerror_(const errinfo_t *tab, size_t tabsz, const char *names, int errnum, char *buff, size_t bufflen, int *err)
 {
 	const errinfo_t *e;
 
@@ -65,25 +65,61 @@ static inline const char *strerror_(const errinfo_t *tab, size_t tabsz, const ch
 	}
 
 	e = bsearch((void *)(long)errnum, tab, tabsz / sizeof(*tab), sizeof(*tab), err_cmp);
-
 	if (e == NULL) {
-		(void)sprintf(err_unknownMsg, "Unknown error %d", errnum);
-		errno = EINVAL;
-		return err_unknownMsg;
-	}
-	else {
-		return names + e->offset;
+		(void)snprintf(buff, bufflen, "Unknown error %d", errnum);
+		*err = EINVAL;
+		return buff;
 	}
+
+	return names + e->offset;
 }
 
 
 char *strerror(int errnum)
 {
-	return (char *)strerror_(errtab, sizeof(errtab), errnames, errnum);
+	static char unknownMsg[32];
+	const char *str;
+	int err = 0;
+
+	str = strerror_(errtab, sizeof(errtab), errnames, errnum, unknownMsg, sizeof(unknownMsg), &err);
+	if (err != 0) {
+		errno = err;
+	}
+
+	return (char *)str;
+}
+
+
+int strerror_r(int errnum, char *buf, size_t buflen)
+{
+	char unknownMsg[32];
+	const char *str;
+	int ret = 0;
+	size_t len;
+
+	str = strerror_(errtab, sizeof(errtab), errnames, errnum, unknownMsg, sizeof(unknownMsg), &ret);
+	len = strlen(str);
+	if (buflen > len) {
+		memcpy(buf, str, len + 1);
+	}
+	else {
+		ret = ERANGE;
+	}
+
+	return ret;
 }
 
 
 const char *gai_strerror(int errnum)
 {
-	return strerror_(gaitab, sizeof(gaitab), gainames, errnum);
+	static char unknownMsg[32];
+	const char *str;
+	int err = 0;
+
+	str = strerror_(gaitab, sizeof(gaitab), gainames, errnum, unknownMsg, sizeof(unknownMsg), &err);
+	if (err != 0) {
+		errno = err;
+	}
+
+	return (char *)str;
 }