system() avoidance: Add lib/proc.c for process manipulation

- Add new functions `proc_runv()` and `proc_runl()`.
- Add new macro `PROC_CMD()`.

include/dao.h

@@ -166,11 +166,17 @@ char *Ctime(const time_t *clock);
 char *Etime(const time_t *clock);
 char *Atime(const time_t *clock);
 char *Now(void);
+/* proc.c */
+int proc_runv(const char *path, const char *argv[]);
+GCC_CHECK_SENTINEL(0) int proc_runl(const char *path, const char *arg0, ...);
 /* xwrite.c */
 int xwrite(int fd, const char *data, int size);
 
 #ifdef __cplusplus
 }  /* extern "C" */
 #endif
 
+/* `proc_runl` without the need of `arg0` and trailing `NULL` */
+#define PROC_CMD(path, ...) proc_runl(path, path, __VA_ARGS__, NULL)
+
 #endif  /* DAO_H */

lib/CMakeLists.txt

@@ -12,6 +12,7 @@ add_library(dao STATIC
     acl.c       chrono32.c  file.c    isnot.c    radix32.c   shm.c
     archiv32.c  dl_lib.c    record.c  splay.c    date_str.c  xsort.c
     attr_lib.c  dns.c       header.c  rfc2047.c  string.c    xwrite.c
+    proc.c
 )
 if(CMAKE_SIZEOF_VOID_P EQUAL 8)
     target_link_libraries(dao PRIVATE -m32)

lib/Makefile

@@ -14,11 +14,13 @@ HDR 	= dao.h dao.p
 
 SRC	= acl.c       chrono32.c  file.c    isnot.c    radix32.c   shm.c   \
 	  archiv32.c  dl_lib.c    record.c  splay.c    date_str.c  xsort.c \
-	  attr_lib.c  dns.c       header.c  rfc2047.c  string.c    xwrite.c
+	  attr_lib.c  dns.c       header.c  rfc2047.c  string.c    xwrite.c \
+	  proc.c
 
 OBJ	= acl.o       chrono32.o  file.o    isnot.o    radix32.o   shm.o   \
 	  archiv32.o  dl_lib.o    record.o  splay.o    date_str.o  xsort.o \
-	  attr_lib.o  dns.o       header.o  rfc2047.o  string.o    xwrite.o
+	  attr_lib.o  dns.o       header.o  rfc2047.o  string.o    xwrite.o \
+	  proc.o
 
 .c.o:   ;$(CC) $(CFLAGS) -c $*.c
 

lib/proc.c

@@ -0,0 +1,78 @@
+/*-------------------------------------------------------*/
+/* lib/proc.c   ( NCKU CCNS WindTop-DreamBBS 3.0 )       */
+/*-------------------------------------------------------*/
+/* Author: [email protected]*/
+/* Target: Process manipulation library for DreamBBS     */
+/* Create: 2020/02/24                                    */
+/*-------------------------------------------------------*/
+
+#include "config.h"
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include "dao.h"
+
+/* `proc_run*()`: Run executable `path` in a child process */
+
+int proc_runv(const char *path, const char *argv[])
+{
+    const pid_t pid = fork();
+
+    switch (pid)
+    {
+    case 0:  // Children
+        execv(path, (char **)argv);
+        exit(127);  // `execv()` failed
+
+    case -1:  // Error
+        return -1;
+
+    default:
+        waitpid(pid, &SINKVAL(int), 0);
+        return 0;
+    }
+}
+
+/* Variadic version for convenience */
+GCC_CHECK_SENTINEL(0)
+int proc_runl(const char *path, const char *arg0, ...)
+{
+    /* Collect args first */
+
+    int argc = 0;
+    int argv_len = 8;
+    const char **argv = (const char **)malloc(sizeof(const char *) * argv_len);
+    const char *ptr;
+    int ret;
+
+    argv[argc++] = arg0;
+
+    if (arg0)
+    {
+        va_list args;
+        va_start(args, arg0);
+        while ((ptr = va_arg(args, const char *)))
+        {
+            argv[argc++] = ptr;
+            if (argc >= argv_len)
+            {
+                const char **argv_new = (const char **)realloc(argv, sizeof(const char *) * (argv_len *= 2));
+                if (!argv_new)
+                    return -1;  // `realloc()` failed
+                argv = argv_new;
+            }
+        }
+        va_end(args);
+
+        argv[argc++] = NULL;
+    }
+
+    /* And then invoke it */
+
+    ret = proc_runv(path, argv);
+    free(argv);
+    return ret;
+}