Add prototype and skeleton of populate_stack() for argument-parsing

Makefile.build

@@ -55,6 +55,7 @@ lib/kernel_SRC += lib/kernel/console.c	# printf(), putchar().
 
 # User process code.
 userprog_SRC  = userprog/process.c	# Process loading.
+userprog_SRC += userprog/populate_stack.c  # Populates stack with program arguments.
 userprog_SRC += userprog/pagedir.c	# Page directories.
 userprog_SRC += userprog/exception.c	# User exception handler.
 userprog_SRC += userprog/syscall.c	# System call handler.

userprog/argument_parsing.h

+#ifndef USERPROG_ARGUMENT_PARSING_H
+#define USERPROG_ARGUMENT_PARSING_H
+
+/*
+ * Given stack pointer `esp`, argument count `argc` and arguments array `argv`,
+ * Populates the stack pointed to by the stack pointer with the given arguments.
+ * TODO: clarify what, if anything, `esp` stands for and rename it to something
+ * clearer if possible.
+ */
+void populate_stack(void* esp, int argc, char** argv);
+
+#endif /* userprog/argument_parsing.h */

userprog/populate_stack.c

+#include "userprog/argument_parsing.h"
+
+
+void populate_stack(void* esp, int argc, char** argv) {
+    #warning "Implement me"
+}