libc: Check for file descriptors 0 and 1, and if they exist do not close and reopen them

libs/libc/include/stdio.h

@@ -32,6 +32,9 @@ extern "C"
     /* Opens the file specified by pathname. Returns the file handle on success, or NULL on error. */
     FILE* fopen(const char* pathname, const char* mode);
 
+    /* Returns a new file associated with the file descriptor fd. */
+    FILE* fdopen(int fd, const char* mode);
+
     /* Writes formatted output according to the string format to the file stream. */
     int fprintf(FILE* stream, const char* format, ...);
 

libs/libc/src/file.cpp

@@ -40,6 +40,19 @@ extern "C"
         return stream;
     }
 
+    FILE* fdopen(int fd, const char*)
+    {
+        if (fd < 0) // FIXME: Also check if the mode string is compatible with how fd was opened.
+        {
+            errno = EBADF;
+            return 0;
+        }
+        FILE* stream = (FILE*)malloc(sizeof(FILE));
+        stream->f_fd = fd;
+        clearerr(stream);
+        return stream;
+    }
+
     size_t fread(void* buf, size_t size, size_t nmemb, FILE* stream)
     {
         ssize_t status = read(stream->f_fd, buf, size * nmemb);

libs/libc/src/init.cpp

@@ -6,13 +6,22 @@
 
 extern "C" void initialize_libc()
 {
-    close(0);  // If it was already open, close it
-    close(1);  // If it was already open, close it
-    errno = 0; // If it was not open. the kernel will throw us EBADF. Let's ignore that, since we don't care.
-    stderr = fopen("/dev/console", "rw");
-    if (!stderr) exit(errno);
-    stdout = fopen("/dev/console", "rw");
-    if (!stdout) exit(errno);
-    clearerr(stderr);
-    clearerr(stdout);
+    if (lseek(0, 0, SEEK_CUR) < 0)
+    {
+        if (errno == EBADF) stdout = fopen("/dev/console", "rw");
+        else
+            exit(errno);
+        if (!stdout) exit(errno);
+        errno = 0;
+    }
+    else { stdout = fdopen(0, "rw"); }
+    if (lseek(1, 0, SEEK_CUR) < 0)
+    {
+        if (errno == EBADF) stderr = fopen("/dev/console", "rw");
+        else
+            exit(errno);
+        if (!stderr) exit(errno);
+        errno = 0;
+    }
+    else { stderr = fdopen(1, "rw"); }
 }