reformat and refactor mkpty.*

cli/mkpty.c

@@ -12,26 +12,18 @@
 #define _XOPEN_SOURCE 600
 /* _GNU_SOURCE unlocks the ptsname_r declaration*/
 #define _GNU_SOURCE
-#include <errno.h>
 #include <fcntl.h>
 #include <stdlib.h>
-#include <unistd.h>
 #include <asm/termbits.h>  /* TIOC* constants */
 #include <sys/ioctl.h>
 
 #include "mkpty.h"
 
-#ifdef PATH_MAX
-# define TTYNAME_MAX PATH_MAX
-#else
-# define TTYNAME_MAX 512
-#endif /* PATH_MAX */
-
 /* Allocate PTY master and slave file descriptors.
  * errno will have been set if newpty() fails.
  *
  * NOTE: This function is my alternative to GLibC's
- * openpty() function. It exists as a learning resource.
+ * NOTE: openpty() function. It exists as a learning resource.
  * REF: https://sourceware.org/git/glibc.git -> ./login/openpty.c
  */
 int mkpty(int *fdmx, int *fds) {
@@ -80,59 +72,63 @@ fail:
 /* Set fdty as the controlling terminal for the calling process.
  * Returns 0 on success, and 1 on failure.
  * NOTE: This function is my alternative to GLibC's
- * login_tty() function. It exists as a learning resource.
+ * NOTE: login_tty() function. It exists as a learning resource.
  * REF: https://sourceware.org/git/glibc.git -> ./login/login_tty.c
+ */
+inline int setctty(const int fdty) {  
+  /* We assume any kernel compiling this defines TIOCSCTTY,
+   * otherwise this implementation won't exactly work... */
+  return (ioctl(fdty, TIOCSCTTY, 0) != -1);
+}
+
+/* Bind fdty (terminal fd) to stdin/stdout/stderr for the calling process. 
+ * This functions blocks until the EBUSY (see `man dup2`) race condition lifts.
+ * NOTE: This function is my alternative to GLibC's
+ * NOTE: login_tty() function. It exists as a learning resource.
  * WARNING: This function maintains the original University of California
  * WARNING: LICENSE (1990-1993) as per glibc.git:/login/login_tty.c
  * WARNING: available at LICENSES/UC-LICENSE in this repo.
+ * REF: https://sourceware.org/git/glibc.git -> ./login/login_tty.c
  */
-int bindpty(const int fdty) {
-  /* We assume any kernel compiling this defines TIOCSCTTY,
-   * otherwise this implementation won't exactly work...
-   */
-  if (ioctl(fdty, TIOCSCTTY, 0) == -1)
-    return EXIT_FAILURE;
-
+inline void bindpty(const int fdty) {
   /* Adjust stdin/stdout/stderr to refer to fd*/
-  while (dup2(fdty, STDIN_FILENO) == -1 && errno == EBUSY)
-    ;
-  while (dup2(fdty, STDOUT_FILENO) == -1 && errno == EBUSY)
-    ;
-  while (dup2(fdty, STDERR_FILENO) == -1 && errno == EBUSY)
-    ;
+  BIND(fdty, STDIN_FILENO);
+  BIND(fdty, STDOUT_FILENO);
+  BIND(fdty, STDERR_FILENO);
   if (fdty > 2)
     close(fdty);
-  
-  return EXIT_SUCCESS;
 }
 
-/* Allocate a PTY and fork, binding the parent to ptmx (master),
- * and the child to pts (slave).
+/* Allocate a PTY and fork, giving ptmx (master) to the parent
+ * and binding the child's stdin/stdout/stderr to pts (slave).
  * Return value is indentical to fork(2).
  * NOTE: This function is my alternative to GLibC's
- * forkpty() function. It exists as a learning resource.
+ * NOTE: forkpty() function. It exists as a learning resource.
  * REF: https://sourceware.org/git/glibc.git -> ./login/forkpty.c
  */
-pid_t forkmkpty(void) {
-  int fdmx, fds;
+pid_t forkmkpty(int *fdmx) {
+  int _fdmx, fds;
   pid_t pid;
-  if (mkpty(&fdmx, &fds))
+  if (mkpty(&_fdmx, &fds))
     return EXIT_FAILURE;
 
   switch (pid = fork()) {
   case -1:
-    close(fdmx);
+    close(_fdmx);
     close(fds);
     return -1;    
   case 0:
     /* Child Process */
-    close(fdmx);
+    close(_fdmx);
+    setctty(fds);
     bindpty(fds);
     break;
     
   default:
     /* Parent Process */
     close(fds);
+    // propagate ptmx (master) fd
+    *fdmx = _fdmx;
     break;
   }
 

cli/mkpty.h

@@ -1,16 +1,30 @@
 #ifndef DORNE_MKPTY_H
 #define DORNE_MKPTY_H
 
+#include <errno.h>
+#include <limits.h>
 #include <sys/types.h>
+#include <unistd.h>
+
+#ifdef PATH_MAX
+#define TTYNAME_MAX PATH_MAX
+#else
+#define TTYNAME_MAX 512
+#endif /* PATH_MAX */
+
+#define BIND(fdsrc, fddst)                                                     \
+  while (dup2(fdsrc, fddst) == -1 && errno == EBUSY)                           \
+    ;
 
 /* Custom implementation of glibc::openpty() */
 int mkpty(int *fdmx, int *fds);
 /* Custom implementation of glibc::login_tty() */
-int bindpty(const int fdty);
+void bindpty(const int fdty);
 /* Custom implementation of glibc::forkpty() */
-pid_t forkmkpty(void);
+pid_t forkmkpty(int *fdmx);
 
-int setptsxy(const unsigned short rows, const unsigned short cols, const int fds);
+int setptsxy(const unsigned short rows, const unsigned short cols,
+             const int fds);
 int getptsxy(unsigned short *rows, unsigned short *cols, const int fds);
 
 #endif /* DORNE_MKPTY_H */