libroot: add ptsname_r for POSIX.1/2024

Change-Id: I9996ff998b2b52a65a101cf7075a3ffb37220962
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8519
Reviewed-by: waddlesplash <[email protected]>

headers/posix/stdlib.h

@@ -183,6 +183,7 @@ extern int		getsubopt(char **optionp, char * const *keylistp,
 extern int		posix_openpt(int openFlags);
 extern int		grantpt(int masterFD);
 extern char*	ptsname(int masterFD);
+extern int		ptsname_r(int masterFD, char *path, size_t maxSize);
 extern int		unlockpt(int masterFD);
 
 /* internal accessor to value for MB_CUR_MAX */

src/system/libroot/posix/stdlib/pty.cpp

@@ -5,6 +5,7 @@
 
 #include <stdlib.h>
 
+#include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
 
@@ -27,19 +28,30 @@ grantpt(int masterFD)
 }
 
 
-char*
+int
-ptsname(int masterFD)
+ptsname_r(int masterFD, char* name, size_t namesize)
 {
 	int32 index;
 	if (ioctl(masterFD, B_IOCTL_GET_TTY_INDEX, &index, sizeof(index)) < 0)
-		return NULL;
+		return errno;
 
-	static char buffer[32];
+	if (name == NULL)
+		return EINVAL;
 
 	char letter = 'p';
-	snprintf(buffer, sizeof(buffer), "/dev/tt/%c%" B_PRIx32,
+	int length = snprintf(name, namesize, "/dev/tt/%c%" B_PRIx32, char(letter + index / 16),
-		char(letter + index / 16), index % 16);
+		index % 16);
+	return (length + 1) > (int)namesize ? ERANGE : 0;
+}
 
+
+char*
+ptsname(int masterFD)
+{
+	static char buffer[32];
+	errno = ptsname_r(masterFD, buffer, sizeof(buffer));
+	if (errno != 0 && errno != ERANGE)
+		return NULL;
 	return buffer;
 }
 
@@ -47,6 +59,7 @@ ptsname(int masterFD)
 int
 unlockpt(int masterFD)
 {
-	// Noting to do ATM.
+	// Nothing to do ATM.
 	return 0;
 }
+