Add public headers

Declarations for the string core, stdio, stdlib, unistd, errno, sys/types, and the raw syscall interface; the FILE layout stays private in src/internal.h.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <[email protected]>

include/errno.h

@@ -0,0 +1,59 @@
+/*
+ * errno.h — error codes for nulsl-libc.
+ *
+ * Single-threaded for now: errno is a plain global. If nulsl-libc ever
+ * grows threads, this becomes a TLS slot or an __errno_location()
+ * indirection without changing any caller.
+ */
+
+#ifndef _NULSL_ERRNO_H
+#define _NULSL_ERRNO_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern int errno;
+
+/* The classic 1-34, values locked by Linux's errno(3) man page. */
+#define EPERM        1  /* Operation not permitted */
+#define ENOENT       2  /* No such file or directory */
+#define ESRCH        3  /* No such process */
+#define EINTR        4  /* Interrupted system call */
+#define EIO          5  /* I/O error */
+#define ENXIO        6  /* No such device or address */
+#define E2BIG        7  /* Argument list too long */
+#define ENOEXEC      8  /* Exec format error */
+#define EBADF        9  /* Bad file descriptor */
+#define ECHILD      10  /* No child processes */
+#define EAGAIN      11  /* Try again */
+#define ENOMEM      12  /* Out of memory */
+#define EACCES      13  /* Permission denied */
+#define EFAULT      14  /* Bad address */
+#define ENOTBLK     15  /* Block device required */
+#define EBUSY       16  /* Device or resource busy */
+#define EEXIST      17  /* File exists */
+#define EXDEV       18  /* Cross-device link */
+#define ENODEV      19  /* No such device */
+#define ENOTDIR     20  /* Not a directory */
+#define EISDIR      21  /* Is a directory */
+#define EINVAL      22  /* Invalid argument */
+#define ENFILE      23  /* File table overflow */
+#define EMFILE      24  /* Too many open files */
+#define ENOTTY      25  /* Not a typewriter */
+#define ETXTBSY     26  /* Text file busy */
+#define EFBIG       27  /* File too large */
+#define ENOSPC      28  /* No space left on device */
+#define ESPIPE      29  /* Illegal seek */
+#define EROFS       30  /* Read-only file system */
+#define EMLINK      31  /* Too many links */
+#define EPIPE       32  /* Broken pipe */
+#define EDOM        33  /* Math argument out of domain */
+#define ERANGE      34  /* Math result not representable */
+#define ENOSYS      38  /* Function not implemented */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _NULSL_ERRNO_H */

include/stdio.h

@@ -0,0 +1,46 @@
+/*
+ * stdio.h — standard I/O for nulsl-libc.
+ *
+ * Minimal for now: unbuffered writes to a file descriptor, plus ENOSYS
+ * stubs for the buffered/formatting machinery that is still to come.
+ * A FILE is just a file descriptor until we grow a real buffering layer.
+ */
+
+#ifndef _NULSL_STDIO_H
+#define _NULSL_STDIO_H
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define EOF (-1)
+
+#define SEEK_SET 0
+#define SEEK_CUR 1
+#define SEEK_END 2
+
+typedef struct nulsl_file FILE;
+
+extern FILE *stdin;
+extern FILE *stdout;
+extern FILE *stderr;
+
+/* Real, unbuffered. */
+int puts(const char *s);
+int putchar(int c);
+
+/* Stubs (see docs/architecture.md for the roadmap). */
+int printf(const char *fmt, ...);
+FILE *fopen(const char *path, const char *mode);
+int fclose(FILE *f);
+size_t fread(void *ptr, size_t size, size_t nmemb, FILE *f);
+size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *f);
+int fflush(FILE *f);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _NULSL_STDIO_H */

include/stdlib.h

@@ -0,0 +1,38 @@
+/*
+ * stdlib.h — general utilities for nulsl-libc.
+ *
+ * The memory functions are ENOSYS stubs until the brk-based allocator
+ * lands; atoi and the exit paths are already real.
+ */
+
+#ifndef _NULSL_STDLIB_H
+#define _NULSL_STDLIB_H
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define EXIT_SUCCESS 0
+#define EXIT_FAILURE 1
+
+/* Stubs: brk()/mmap() allocator is on the roadmap. */
+void *malloc(size_t size);
+void *calloc(size_t nmemb, size_t size);
+void *realloc(void *ptr, size_t size);
+void free(void *ptr);
+
+/* Real. */
+void exit(int status);
+void abort(void);
+int atoi(const char *s);
+
+/* Stub. */
+long strtol(const char *s, char **endptr, int base);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _NULSL_STDLIB_H */

include/string.h

@@ -0,0 +1,32 @@
+/*
+ * string.h — memory and string operations.
+ *
+ * All functions here are real, tiny, and freestanding: no libc, no
+ * compiler builtins. They are the foundation everything else builds on.
+ */
+
+#ifndef _NULSL_STRING_H
+#define _NULSL_STRING_H
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+size_t strlen(const char *s);
+int strcmp(const char *a, const char *b);
+int strncmp(const char *a, const char *b, size_t n);
+char *strcpy(char *dst, const char *src);
+char *strncpy(char *dst, const char *src, size_t n);
+
+void *memcpy(void *restrict dst, const void *restrict src, size_t n);
+void *memmove(void *dst, const void *src, size_t n);
+void *memset(void *dst, int c, size_t n);
+int memcmp(const void *a, const void *b, size_t n);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _NULSL_STRING_H */

include/sys/syscall.h

@@ -0,0 +1,51 @@
+/*
+ * sys/syscall.h — the raw syscall interface.
+ *
+ * syscall() is the ONLY place in nulsl-libc that talks the kernel ABI.
+ * Everything above it (read, write, exit, ...) is a wrapper.
+ *
+ * SYS_* constants below are the x86_64 numbers for the syscalls the libc
+ * itself wraps or its tests use. They are #ifndef-guarded so kernel UAPI
+ * headers can coexist. Extend the table as needed (docs/syscalls.md).
+ */
+
+#ifndef _NULSL_SYS_SYSCALL_H
+#define _NULSL_SYS_SYSCALL_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+long syscall(long number, ...);
+
+/* x86_64 syscall numbers (Linux ABI). */
+#ifndef SYS_read
+#define SYS_read 0
+#endif
+#ifndef SYS_write
+#define SYS_write 1
+#endif
+#ifndef SYS_open
+#define SYS_open 2
+#endif
+#ifndef SYS_close
+#define SYS_close 3
+#endif
+#ifndef SYS_getpid
+#define SYS_getpid 39
+#endif
+#ifndef SYS_exit
+#define SYS_exit 60
+#endif
+#ifndef SYS_unlink
+#define SYS_unlink 87
+#endif
+#ifndef SYS_clock_gettime
+#define SYS_clock_gettime 228
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _NULSL_SYS_SYSCALL_H */

include/sys/types.h

@@ -0,0 +1,25 @@
+/*
+ * sys/types.h — primitive system types for nulsl-libc.
+ */
+
+#ifndef _NULSL_SYS_TYPES_H
+#define _NULSL_SYS_TYPES_H
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef long ssize_t;
+typedef long off_t;
+typedef long pid_t;
+typedef unsigned int uid_t;
+typedef unsigned int gid_t;
+typedef unsigned long mode_t;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _NULSL_SYS_TYPES_H */

include/unistd.h

@@ -0,0 +1,38 @@
+/*
+ * unistd.h — POSIX system call wrappers for nulsl-libc.
+ *
+ * These are thin, real wrappers around the raw syscall() interface — see
+ * docs/syscalls.md. The kernel is the API; everything else is sugar.
+ */
+
+#ifndef _NULSL_UNISTD_H
+#define _NULSL_UNISTD_H
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define STDIN_FILENO  0
+#define STDOUT_FILENO 1
+#define STDERR_FILENO 2
+
+/* Real syscall wrappers. */
+ssize_t read(int fd, void *buf, size_t count);
+ssize_t write(int fd, const void *buf, size_t count);
+int close(int fd);
+pid_t getpid(void);
+void _exit(int status) __attribute__((noreturn));
+
+/* Stub. */
+int unlink(const char *path);
+
+/* Raw syscall entry point (also available here for convenience). */
+long syscall(long number, ...);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _NULSL_UNISTD_H */