Switch to pragma once for all header files (#39)

ryuukumar · web-flow · commit f9d964cf2344 · 2026-04-14T20:32:17.000+05:30
* Move from explicit define calls to pragma once

* Same for kclib

* Add 'On cross-compilers' section to readme
diff --git a/README.md b/README.md
@@ -26,6 +26,10 @@ In order from `critical` to `meh`:
 - [optional] `doxygen` for documentation (`sudo apt install doxygen` or similar)
 - [optional] `qemu-system-x86` if you want to use `qemu.sh` to run COS (`sudo apt install qemu-system-x86` or similar)
 
+#### On cross-compilers
+
+COS has been written keeping in mind the capabilities and conventions of GNU C23. It is strongly recommended to compile a GCC for compiling COS, and this requirement has been enforced in build.sh. Use other compilers at your own risk.
+
 ### Actually building (and running) COS
 
 You can run the following code to download and build COS:
diff --git a/kernel/include/kclib/ctype.h b/kernel/include/kclib/ctype.h
@@ -1,5 +1,4 @@
-#ifndef CTYPE_H
-#define CTYPE_H
+#pragma once
 
 int isalnum (int c);
 int isalpha (int c);
@@ -16,5 +15,3 @@ int ispunct (int c);
 
 int tolower (int c);
 int toupper (int c);
-
-#endif
diff --git a/kernel/include/kclib/stdio.h b/kernel/include/kclib/stdio.h
@@ -1,5 +1,4 @@
-#ifndef STDIO_H
-#define STDIO_H
+#pragma once
 
 #include <kernel/console.h>
 #include <stdarg.h>
@@ -11,5 +10,3 @@ void ksprintf (char* buf, const char* fmt, ...);
 void kprintf (const char*, ...);
 
 void kserial_printf (const char* fmt, ...);
-
-#endif
diff --git a/kernel/include/kclib/string.h b/kernel/include/kclib/string.h
@@ -1,5 +1,4 @@
-#ifndef STRING_H
-#define STRING_H
+#pragma once
 
 #include <stddef.h>
 #include <stdint.h>
@@ -44,5 +43,3 @@ char* kstrtok_r (char* restrict s1, const char* restrict s2, char** restrict sav
 
 void kitos (int32_t i, char* buf, uint32_t b);
 void kulitos (uint64_t i, char* buf, uint32_t b);
-
-#endif
diff --git a/kernel/include/kernel/console.h b/kernel/include/kernel/console.h
@@ -1,5 +1,4 @@
-#ifndef CONSOLE_H
-#define CONSOLE_H
+#pragma once
 
 #include <stdbool.h>
 #include <stddef.h>
@@ -18,5 +17,3 @@ void update (void);
 
 void putchar (unsigned char);
 void putstr (const char*, size_t);
-
-#endif
diff --git a/kernel/include/kernel/elf.h b/kernel/include/kernel/elf.h
@@ -1,5 +1,4 @@
-#ifndef ELF_H
-#define ELF_H
+#pragma once
 
 #include <kernel/process.h>
 #include <stdbool.h>
@@ -56,5 +55,3 @@ typedef struct __attribute__ ((packed)) {
 
 bool verify_elf_loadable (elf64_header_t* elf);
 int	 load_elf (const char* filepath, process* target_process, uintptr_t* entry_point_r);
-
-#endif
diff --git a/kernel/include/kernel/error.h b/kernel/include/kernel/error.h
@@ -1,5 +1,4 @@
-#ifndef ERROR_H
-#define ERROR_H
+#pragma once
 
 // Invalid argument
 #define EINVARG 100
@@ -28,5 +27,3 @@
 
 // Cannot execute
 #define ENOEXEC 701
-
-#endif
diff --git a/kernel/include/kernel/fs/chardev.h b/kernel/include/kernel/fs/chardev.h
@@ -1,8 +1,5 @@
-#ifndef CHAR_DEV_H
-#define CHAR_DEV_H
+#pragma once
 
 #include <kernel/fs/vfs.h>
 
 void init_tty1 (inode* absolute_root);
-
-#endif
diff --git a/kernel/include/kernel/fs/cpio.h b/kernel/include/kernel/fs/cpio.h
@@ -1,5 +1,4 @@
-#ifndef CPIO_H
-#define CPIO_H
+#pragma once
 
 #include <kernel/fs/vfs.h>
 #include <stddef.h>
@@ -23,5 +22,3 @@ typedef struct {
 } cpio_newc_header_t;
 
 int load_cpio_from_memory (void* pos, const char* out_path);
-
-#endif
diff --git a/kernel/include/kernel/fs/ramfs.h b/kernel/include/kernel/fs/ramfs.h
@@ -1,5 +1,4 @@
-#ifndef RAMFS_H
-#define RAMFS_H
+#pragma once
 
 #include <kernel/fs/vfs.h>
 
@@ -27,5 +26,3 @@ typedef struct {
 } fs_info_t;
 
 inode* init_ramfs_root (void);
-
-#endif
diff --git a/kernel/include/kernel/fs/vfs.h b/kernel/include/kernel/fs/vfs.h
@@ -1,5 +1,4 @@
-#ifndef VFS_H
-#define VFS_H
+#pragma once
 
 #include <stddef.h>
 #include <stdint.h>
@@ -70,5 +69,3 @@ uint64_t sys_mkdir (uint64_t path, uint64_t mode, uint64_t arg3);
 
 inode* get_absolute_root (void);
 void   init_vfs (inode* absolute_root);
-
-#endif
diff --git a/kernel/include/kernel/gdt.h b/kernel/include/kernel/gdt.h
@@ -1,4 +1,5 @@
 #pragma once
+
 #include <stdint.h>
 
 typedef struct __attribute__ ((packed)) {
@@ -55,4 +56,4 @@ void init_tss (void);
 void tss_set_stack (uintptr_t stack);
 
 extern void gdt_flush (gdt_pointer_t*);
-extern void tss_flush (void);
+extern void tss_flush (void);
diff --git a/kernel/include/kernel/graphics.h b/kernel/include/kernel/graphics.h
@@ -1,5 +1,4 @@
-#ifndef GRAPHICS_H
-#define GRAPHICS_H
+#pragma once
 
 #include <kernel/limine.h>
 #include <stddef.h>
@@ -16,5 +15,3 @@ size_t		postoi (int, int);
 void renderGlyph (unsigned char*, int, int, size_t, size_t, int, uint32_t);
 
 void drawBorder (size_t);
-
-#endif
diff --git a/kernel/include/kernel/handlers.h b/kernel/include/kernel/handlers.h
@@ -1,11 +1,6 @@
-
-#ifndef HANDLERS_H
-#define HANDLERS_H
+#pragma once
 
 #include <kernel/idt.h>
 
 void handle_gpf (registers_t* registers);
-
 void init_handlers (void);
-
-#endif
diff --git a/kernel/include/kernel/hardfonts/classic.h b/kernel/include/kernel/hardfonts/classic.h
@@ -1,6 +1,3 @@
-#ifndef CLASSIC_H
-#define CLASSIC_H
+#pragma once
 
 unsigned char* glyph (char index);
-
-#endif
diff --git a/kernel/include/kernel/hw/pic.h b/kernel/include/kernel/hw/pic.h
@@ -1,6 +1,4 @@
-
-#ifndef PIC_H
-#define PIC_H
+#pragma once
 
 #include <kernel/io.h>
 #include <stdint.h>
@@ -19,5 +17,3 @@ void pic_clr_mask (uint8_t irq_line);
 void pic_send_eoi (uint8_t irq);
 
 void init_pic (void);
-
-#endif
diff --git a/kernel/include/kernel/hw/timer.h b/kernel/include/kernel/hw/timer.h
@@ -1,11 +1,8 @@
-#ifndef TIMER_H
-#define TIMER_H
+#pragma once
 
 #include <kernel/idt.h>
 
 uint64_t get_current_tick (void);
 
 void timer_handler (registers_t* registers);
 void init_timer (void);
-
-#endif
diff --git a/kernel/include/kernel/idt.h b/kernel/include/kernel/idt.h
@@ -1,6 +1,4 @@
-
-#ifndef IDT_H
-#define IDT_H
+#pragma once
 
 #include <stdint.h>
 
@@ -35,5 +33,3 @@ typedef void (*irq_handler_t) (registers_t*);
 void init_idt (void);
 void idt_register_handler (int vector, irq_handler_t handler);
 void idt_set_flags (int vector, uint8_t gate_type, uint8_t dpl, uint8_t ist);
-
-#endif
diff --git a/kernel/include/kernel/io.h b/kernel/include/kernel/io.h
@@ -1,6 +1,4 @@
-
-#ifndef IO_H
-#define IO_H
+#pragma once
 
 #include <stdint.h>
 
@@ -10,5 +8,3 @@ void	io_wait (void);
 
 uint64_t save_irq_disable (void);
 void	 restore_irq (uint64_t flags);
-
-#endif
diff --git a/kernel/include/kernel/memmgt.h b/kernel/include/kernel/memmgt.h
@@ -1,5 +1,4 @@
-#ifndef MEMMGT_H
-#define MEMMGT_H
+#pragma once
 
 #include <kernel/limine.h>
 #include <stdbool.h>
@@ -121,5 +120,3 @@ int	  liballoc_lock (void);
 int	  liballoc_unlock (void);
 void* liballoc_alloc (size_t);
 int	  liballoc_free (void*, size_t);
-
-#endif
diff --git a/kernel/include/kernel/process.h b/kernel/include/kernel/process.h
@@ -1,5 +1,4 @@
-#ifndef PROCESS_H
-#define PROCESS_H
+#pragma once
 
 #include <kernel/fs/vfs.h>
 #include <kernel/idt.h>
@@ -41,5 +40,3 @@ void schedule (registers_t* registers);
 int process_fork (process* source_process, process** dest_ptr);
 
 void init_process (void);
-
-#endif
diff --git a/kernel/include/kernel/serial.h b/kernel/include/kernel/serial.h
@@ -1,6 +1,4 @@
-
-#ifndef SERIAL_H
-#define SERIAL_H
+#pragma once
 
 #define SERIAL_COM_1 0x3F8
 
@@ -13,5 +11,3 @@ int init_serial (void);
 uint8_t read_serial (void);
 void	write_serial (uint8_t val);
 void	write_serial_str (const char* str);
-
-#endif
diff --git a/kernel/include/kernel/syscall.h b/kernel/include/kernel/syscall.h
@@ -1,6 +1,4 @@
-
-#ifndef SYSCALL_H
-#define SYSCALL_H
+#pragma once
 
 #include <kernel/idt.h>
 
@@ -26,5 +24,3 @@ void init_syscalls (void);
 void		 register_syscall (int vector, syscall_handler_t handler);
 uint64_t	 do_syscall (uint64_t syscall, uint64_t arg1, uint64_t arg2, uint64_t arg3);
 registers_t* get_latest_r_frame (void);
-
-#endif
diff --git a/kernel/include/utils/charqueue.h b/kernel/include/utils/charqueue.h
@@ -1,5 +1,4 @@
-#ifndef CHARQUEUE_H
-#define CHARQUEUE_H
+#pragma once
 
 #include <kernel/memmgt.h>
 
@@ -26,5 +25,3 @@ int		   free_charqueue (charqueue* queue);
 int push_charqueue (charqueue* queue, unsigned char insert);
 int pop_charqueue (charqueue* queue, unsigned char* ret);
 int peek_charqueue (charqueue* queue, unsigned char* ret);
-
-#endif
diff --git a/kernel/include/utils/spinlock.h b/kernel/include/utils/spinlock.h
@@ -1,7 +1,4 @@
-#ifndef SPINLOCK_H
-#define SPINLOCK_H
+#pragma once
 
 uint64_t spinlock_acquire (bool* lock);
 void	 spinlock_release (bool* lock, uint64_t flags);
-
-#endif
