libc: Implement freopen()

That function was severely outdated.

apps/src/init.c

@@ -174,6 +174,14 @@ int main()
     }
     else { printf("Success!! Got PID %ld\n", child); }
 
+    child = fork();
+    if (child < 0)
+    {
+        perror("fork");
+        return 1;
+    }
+    if (child == 0) { *(int*)(0xdeadbeef) = 1234; }
+
     int status;
     for (;;)
     {

kernel/src/interrupts/Entry.cpp

@@ -51,8 +51,6 @@ extern "C" void common_handler(Context* context)
             StackTracer tracer(context->rbp);
             tracer.trace_with_ip(context->rip);
 
-            hang(); // FIXME: Remove this when multiple address spaces are working.
-
             Scheduler::task_misbehave(context, -3);
         }
     }

kernel/src/thread/Scheduler.cpp

@@ -287,8 +287,17 @@ void Scheduler::task_misbehave(Context* context, int64_t status)
 {
     ASSERT(Interrupts::is_in_handler());
     kdbgln("exit: task %ld misbehaved, used %ld ms of cpu time", sched_current_task->id, sched_current_task->cpu_time);
-    sched_current_task->state = sched_current_task->Exited;
+    if (sched_current_task->id == 1) sched_current_task->state = sched_current_task->Exited;
+    else
+        sched_current_task->state = sched_current_task->Dying;
     sched_current_task->exit_status = status;
+    if (sched_current_task->id != 1)
+    {
+        sched_for_each_child(sched_current_task, [](Task* child) {
+            if (child->state != child->Exited) child->ppid = 1;
+            return true;
+        });
+    }
     task_yield(context);
 }
 

libs/libc/include/stdio.h

@@ -42,6 +42,9 @@ extern "C"
     /* Returns a new file associated with the file descriptor fd. */
     FILE* fdopen(int fd, const char* mode);
 
+    /* Opens the file specified by pathname and points the file handle stream to it. */
+    FILE* freopen(const char* pathname, const char* mode, FILE* stream);
+
     /* Returns the file descriptor associated with the file stream. */
     int fileno(FILE* stream);
 

libs/libc/src/file.cpp

@@ -51,6 +51,20 @@ extern "C"
         return stream;
     }
 
+    FILE* freopen(const char* pathname, const char* mode,
+                  FILE* stream) // FIXME: If pathname is NULL, open the original file with the new mode.
+    {
+        int fd = open(pathname, O_RDWR); // FIXME: Use the mode string.
+        if (fd < 0) { return 0; }
+
+        fflush(stream); // To make it future-proof.
+        fclose(stream);
+
+        stream->f_fd = fd;
+        clearerr(stream);
+        return stream;
+    }
+
     int fileno(FILE* stream)
     {
         return stream->f_fd;