feat(errno): public errno.h with strerror/strerror_r

include/errno.h

@@ -0,0 +1,229 @@
+#ifndef VLIBC_ERRNO_H
+#define VLIBC_ERRNO_H
+
+/*
+ * vlibc — <errno.h>.
+ *
+ * errno is per-thread state. It lives in a slot of the thread control block
+ * (TCB), addressed relative to the x86_64 FS thread pointer; there is no
+ * process-global errno object and no compiler-managed TLS (`__thread`) here.
+ * The errno macro below expands to a dereference of __errno_location(), the
+ * implementation-reserved accessor that returns the address of the calling
+ * thread's errno slot. The offset of that slot inside the TCB is the ABI
+ * constant VLIBC_TCB_ERRNO_OFF, owned by the internal TCB/ABI headers (see
+ * src/internal/errno.h) — this public header is the single canonical home
+ * for the errno macro, the __errno_location() declaration, and the E*
+ * constant table, so internal code includes it instead of keeping a copy.
+ *
+ * Levels are cumulative (see include/vlibc/features.h):
+ *   Level 1 (onlyposix): POSIX base — strerror.
+ *   Level 2 (muslmimic): XSI — strerror_r (the int-returning flavor; the
+ *                        GNU char*-returning variant is level 3+ and is
+ *                        deliberately not provided).
+ *
+ * This header includes <vlibc/features.h> itself, so the gates below always
+ * see the configured VLIBC_LEVEL even when the caller included no vlibc
+ * header first, and <stddef.h> for size_t.
+ */
+
+#include <vlibc/features.h>
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Return the address of the calling thread's errno slot.
+ *
+ * Requires the thread pointer (FS) to be initialized to a TCB whose first
+ * word is the TCB's own address — the startup todo owns that bootstrap and
+ * sets it before any code that can touch errno runs. This function itself
+ * performs no setup and no other TCB access.
+ *
+ * The name sits in the implementation-reserved namespace deliberately: it is
+ * this libc's private errno accessor, not public API.
+ */
+int *
+__errno_location(void); // NOLINT(bugprone-reserved-identifier)
+
+/* The conventional errno lvalue; resolves to the caller's TCB slot. */
+#define errno (*__errno_location())
+
+/*
+ * Error numbers: the Linux errno ABI (asm-generic/errno-base.h plus
+ * asm-generic/errno.h, which is the table x86_64 uses), transcribed as
+ * kernel-ABI facts. These values are fixed and shared with the kernel.
+ * Values 41 and 58 do not exist in the ABI (EWOULDBLOCK and EDEADLOCK are
+ * aliases of EAGAIN and EDEADLK); EHWPOISON is the last defined value.
+ */
+
+#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 of func */
+#define ERANGE 34           /* Math result not representable */
+#define EDEADLK 35          /* Resource deadlock would occur */
+#define ENAMETOOLONG 36     /* File name too long */
+#define ENOLCK 37           /* No record locks available */
+#define ENOSYS 38           /* Invalid system call number */
+#define ENOTEMPTY 39        /* Directory not empty */
+#define ELOOP 40            /* Too many symbolic links encountered */
+#define EWOULDBLOCK EAGAIN  /* Operation would block */
+#define ENOMSG 42           /* No message of desired type */
+#define EIDRM 43            /* Identifier removed */
+#define ECHRNG 44           /* Channel number out of range */
+#define EL2NSYNC 45         /* Level 2 not synchronized */
+#define EL3HLT 46           /* Level 3 halted */
+#define EL3RST 47           /* Level 3 reset */
+#define ELNRNG 48           /* Link number out of range */
+#define EUNATCH 49          /* Protocol driver not attached */
+#define ENOCSI 50           /* No CSI structure available */
+#define EL2HLT 51           /* Level 2 halted */
+#define EBADE 52            /* Invalid exchange */
+#define EBADR 53            /* Invalid request descriptor */
+#define EXFULL 54           /* Exchange full */
+#define ENOANO 55           /* No anode */
+#define EBADRQC 56          /* Invalid request code */
+#define EBADSLT 57          /* Invalid slot */
+#define EDEADLOCK EDEADLK   /* File locking deadlock error */
+#define EBFONT 59           /* Bad font file format */
+#define ENOSTR 60           /* Device not a stream */
+#define ENODATA 61          /* No data available */
+#define ETIME 62            /* Timer expired */
+#define ENOSR 63            /* Out of streams resources */
+#define ENONET 64           /* Machine is not on the network */
+#define ENOPKG 65           /* Package not installed */
+#define EREMOTE 66          /* Object is remote */
+#define ENOLINK 67          /* Link has been severed */
+#define EADV 68             /* Advertise error */
+#define ESRMNT 69           /* Srmount error */
+#define ECOMM 70            /* Communication error on send */
+#define EPROTO 71           /* Protocol error */
+#define EMULTIHOP 72        /* Multihop attempted */
+#define EDOTDOT 73          /* RFS specific error */
+#define EBADMSG 74          /* Not a data message */
+#define EOVERFLOW 75        /* Value too large for defined data type */
+#define ENOTUNIQ 76         /* Name not unique on network */
+#define EBADFD 77           /* File descriptor in bad state */
+#define EREMCHG 78          /* Remote address changed */
+#define ELIBACC 79          /* Can not access a needed shared library */
+#define ELIBBAD 80          /* Accessing a corrupted shared library */
+#define ELIBSCN 81          /* .lib section in a.out corrupted */
+#define ELIBMAX 82          /* Attempting to link in too many shared libraries */
+#define ELIBEXEC 83         /* Cannot exec a shared library directly */
+#define EILSEQ 84           /* Illegal byte sequence */
+#define ERESTART 85         /* Interrupted system call should be restarted */
+#define ESTRPIPE 86         /* Streams pipe error */
+#define EUSERS 87           /* Too many users */
+#define ENOTSOCK 88         /* Socket operation on non-socket */
+#define EDESTADDRREQ 89     /* Destination address required */
+#define EMSGSIZE 90         /* Message too long */
+#define EPROTOTYPE 91       /* Protocol wrong type for socket */
+#define ENOPROTOOPT 92      /* Protocol not available */
+#define EPROTONOSUPPORT 93  /* Protocol not supported */
+#define ESOCKTNOSUPPORT 94  /* Socket type not supported */
+#define EOPNOTSUPP 95       /* Operation not supported on transport endpoint */
+#define EPFNOSUPPORT 96     /* Protocol family not supported */
+#define EAFNOSUPPORT 97     /* Address family not supported by protocol */
+#define EADDRINUSE 98       /* Address already in use */
+#define EADDRNOTAVAIL 99    /* Cannot assign requested address */
+#define ENETDOWN 100        /* Network is down */
+#define ENETUNREACH 101     /* Network is unreachable */
+#define ENETRESET 102       /* Network dropped connection because of reset */
+#define ECONNABORTED 103    /* Software caused connection abort */
+#define ECONNRESET 104      /* Connection reset by peer */
+#define ENOBUFS 105         /* No buffer space available */
+#define EISCONN 106         /* Transport endpoint is already connected */
+#define ENOTCONN 107        /* Transport endpoint is not connected */
+#define ESHUTDOWN 108       /* Cannot send after transport endpoint shutdown */
+#define ETOOMANYREFS 109    /* Too many references: cannot splice */
+#define ETIMEDOUT 110       /* Connection timed out */
+#define ECONNREFUSED 111    /* Connection refused */
+#define EHOSTDOWN 112       /* Host is down */
+#define EHOSTUNREACH 113    /* No route to host */
+#define EALREADY 114        /* Operation already in progress */
+#define EINPROGRESS 115     /* Operation now in progress */
+#define ESTALE 116          /* Stale file handle */
+#define EUCLEAN 117         /* Structure needs cleaning */
+#define ENOTNAM 118         /* Not a XENIX named type file */
+#define ENAVAIL 119         /* No XENIX semaphores available */
+#define EISNAM 120          /* Is a named type file */
+#define EREMOTEIO 121       /* Remote I/O error */
+#define EDQUOT 122          /* Quota exceeded */
+#define ENOMEDIUM 123       /* No medium found */
+#define EMEDIUMTYPE 124     /* Wrong medium type */
+#define ECANCELED 125       /* Operation canceled */
+#define ENOKEY 126          /* Required key not available */
+#define EKEYEXPIRED 127     /* Key has expired */
+#define EKEYREVOKED 128     /* Key has been revoked */
+#define EKEYREJECTED 129    /* Key was rejected by service */
+#define EOWNERDEAD 130      /* Owner died */
+#define ENOTRECOVERABLE 131 /* State not recoverable */
+#define ERFKILL 132         /* Operation not possible due to RF-kill */
+#define EHWPOISON 133       /* Memory page has hardware error */
+
+/*
+ * Return a pointer to the message string for errnum. The string for a known
+ * value points to immutable static storage and is safe to keep across calls;
+ * an unknown value yields "Unknown error <errnum>", formatted into shared
+ * static storage whose contents a later call may overwrite (unknown errno
+ * values are a rare diagnostic path; see strerror.c). Never returns NULL.
+ *
+ * No intent attribute: the unknown-value path writes shared storage.
+ */
+char *
+strerror(int errnum);
+
+#if VLIBC_LEVEL_GE(2)
+/* Level 2 (muslmimic): XSI. */
+
+/*
+ * XSI strerror_r: copy the message for errnum into buf, truncated to buflen
+ * and always NUL-terminated when buflen > 0, and return 0 — including for
+ * unknown errnum values, whose text is "Unknown error <errnum>". When buflen
+ * is 0 nothing is written and 0 is returned; when buf is NULL and buflen > 0,
+ * EINVAL is returned. The GNU char*-returning variant is deliberately not
+ * provided.
+ *
+ * No intent attribute: it writes memory.
+ */
+int
+strerror_r(int errnum, char *buf, size_t buflen);
+#endif /* VLIBC_LEVEL_GE(2) */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* VLIBC_ERRNO_H */

src/errno/strerror.c

@@ -0,0 +1,296 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <errno.h>
+
+/*
+ * vlibc — strerror / strerror_r (todo 2).
+ *
+ * strerror maps an errno value to an informative, descriptive message. The
+ * messages are this libc's own standard English texts (they need not match
+ * glibc verbatim). Known values resolve to immutable static string constants;
+ * unknown values resolve to "Unknown error <N>" with <N> formatted in place.
+ *
+ * Thread-safety of the unknown-value path: the formatted string lives in a
+ * single static buffer, so two threads formatting *unknown* errno values
+ * concurrently can observe each other's text. This tradeoff is deliberate at
+ * this stage: unknown errno values are a rare diagnostic path, the library
+ * has no per-thread storage beyond the errno TCB slot yet, and strerror must
+ * not depend on malloc (or any other subsystem). The pointer returned for
+ * known values is unaffected. Once the real TCB layout lands (startup todo),
+ * this can migrate to a per-thread buffer without changing the interface.
+ *
+ * The unknown-value formatter is hand-rolled: strerror is libc base and must
+ * not pull in stdio/string before those exist.
+ */
+
+/*
+ * Message table: one entry per defined E* value, indexed directly by the
+ * errno number. Designated initializers keep name/value pairs provably in
+ * sync with <errno.h>; entries for the ABI gaps (41, 58 — values the kernel
+ * never produces) stay NULL and are treated as unknown. EWOULDBLOCK and
+ * EDEADLOCK are aliases of EAGAIN and EDEADLK, so they share those entries.
+ * The array auto-sizes to EHWPOISON + 1 (134) entries.
+ */
+static const char *const errmsg[] = {
+    [0] = "Success",
+    [EPERM] = "Operation not permitted",
+    [ENOENT] = "No such file or directory",
+    [ESRCH] = "No such process",
+    [EINTR] = "Interrupted system call",
+    [EIO] = "Input/output error",
+    [ENXIO] = "No such device or address",
+    [E2BIG] = "Argument list too long",
+    [ENOEXEC] = "Exec format error",
+    [EBADF] = "Bad file descriptor",
+    [ECHILD] = "No child processes",
+    [EAGAIN] = "Resource temporarily unavailable",
+    [ENOMEM] = "Cannot allocate memory",
+    [EACCES] = "Permission denied",
+    [EFAULT] = "Bad address",
+    [ENOTBLK] = "Block device required",
+    [EBUSY] = "Device or resource busy",
+    [EEXIST] = "File exists",
+    [EXDEV] = "Invalid cross-device link",
+    [ENODEV] = "No such device",
+    [ENOTDIR] = "Not a directory",
+    [EISDIR] = "Is a directory",
+    [EINVAL] = "Invalid argument",
+    [ENFILE] = "Too many open files in system",
+    [EMFILE] = "Too many open files",
+    [ENOTTY] = "Inappropriate ioctl for device",
+    [ETXTBSY] = "Text file busy",
+    [EFBIG] = "File too large",
+    [ENOSPC] = "No space left on device",
+    [ESPIPE] = "Illegal seek",
+    [EROFS] = "Read-only file system",
+    [EMLINK] = "Too many links",
+    [EPIPE] = "Broken pipe",
+    [EDOM] = "Numerical argument out of domain",
+    [ERANGE] = "Numerical result out of range",
+    [EDEADLK] = "Resource deadlock would occur",
+    [ENAMETOOLONG] = "File name too long",
+    [ENOLCK] = "No locks available",
+    [ENOSYS] = "Function not implemented",
+    [ENOTEMPTY] = "Directory not empty",
+    [ELOOP] = "Too many levels of symbolic links",
+    [ENOMSG] = "No message of desired type",
+    [EIDRM] = "Identifier removed",
+    [ECHRNG] = "Channel number out of range",
+    [EL2NSYNC] = "Level 2 not synchronized",
+    [EL3HLT] = "Level 3 halted",
+    [EL3RST] = "Level 3 reset",
+    [ELNRNG] = "Link number out of range",
+    [EUNATCH] = "Protocol driver not attached",
+    [ENOCSI] = "No CSI structure available",
+    [EL2HLT] = "Level 2 halted",
+    [EBADE] = "Invalid exchange",
+    [EBADR] = "Invalid request descriptor",
+    [EXFULL] = "Exchange full",
+    [ENOANO] = "No anode",
+    [EBADRQC] = "Invalid request code",
+    [EBADSLT] = "Invalid slot",
+    [EBFONT] = "Bad font file format",
+    [ENOSTR] = "Device not a stream",
+    [ENODATA] = "No data available",
+    [ETIME] = "Timer expired",
+    [ENOSR] = "Out of streams resources",
+    [ENONET] = "Machine is not on the network",
+    [ENOPKG] = "Package not installed",
+    [EREMOTE] = "Object is remote",
+    [ENOLINK] = "Link has been severed",
+    [EADV] = "Advertise error",
+    [ESRMNT] = "Srmount error",
+    [ECOMM] = "Communication error on send",
+    [EPROTO] = "Protocol error",
+    [EMULTIHOP] = "Multihop attempted",
+    [EDOTDOT] = "RFS specific error",
+    [EBADMSG] = "Bad message",
+    [EOVERFLOW] = "Value too large for defined data type",
+    [ENOTUNIQ] = "Name not unique on network",
+    [EBADFD] = "File descriptor in bad state",
+    [EREMCHG] = "Remote address changed",
+    [ELIBACC] = "Can not access a needed shared library",
+    [ELIBBAD] = "Accessing a corrupted shared library",
+    [ELIBSCN] = ".lib section in a.out corrupted",
+    [ELIBMAX] = "Attempting to link in too many shared libraries",
+    [ELIBEXEC] = "Cannot exec a shared library directly",
+    [EILSEQ] = "Invalid or incomplete multibyte or wide character",
+    [ERESTART] = "Interrupted system call should be restarted",
+    [ESTRPIPE] = "Streams pipe error",
+    [EUSERS] = "Too many users",
+    [ENOTSOCK] = "Socket operation on non-socket",
+    [EDESTADDRREQ] = "Destination address required",
+    [EMSGSIZE] = "Message too long",
+    [EPROTOTYPE] = "Protocol wrong type for socket",
+    [ENOPROTOOPT] = "Protocol not available",
+    [EPROTONOSUPPORT] = "Protocol not supported",
+    [ESOCKTNOSUPPORT] = "Socket type not supported",
+    [EOPNOTSUPP] = "Operation not supported",
+    [EPFNOSUPPORT] = "Protocol family not supported",
+    [EAFNOSUPPORT] = "Address family not supported by protocol",
+    [EADDRINUSE] = "Address already in use",
+    [EADDRNOTAVAIL] = "Cannot assign requested address",
+    [ENETDOWN] = "Network is down",
+    [ENETUNREACH] = "Network is unreachable",
+    [ENETRESET] = "Network dropped connection on reset",
+    [ECONNABORTED] = "Software caused connection abort",
+    [ECONNRESET] = "Connection reset by peer",
+    [ENOBUFS] = "No buffer space available",
+    [EISCONN] = "Transport endpoint is already connected",
+    [ENOTCONN] = "Transport endpoint is not connected",
+    [ESHUTDOWN] = "Cannot send after transport endpoint shutdown",
+    [ETOOMANYREFS] = "Too many references: cannot splice",
+    [ETIMEDOUT] = "Connection timed out",
+    [ECONNREFUSED] = "Connection refused",
+    [EHOSTDOWN] = "Host is down",
+    [EHOSTUNREACH] = "No route to host",
+    [EALREADY] = "Operation already in progress",
+    [EINPROGRESS] = "Operation now in progress",
+    [ESTALE] = "Stale file handle",
+    [EUCLEAN] = "Structure needs cleaning",
+    [ENOTNAM] = "Not a XENIX named type file",
+    [ENAVAIL] = "No XENIX semaphores available",
+    [EISNAM] = "Is a named type file",
+    [EREMOTEIO] = "Remote I/O error",
+    [EDQUOT] = "Disk quota exceeded",
+    [ENOMEDIUM] = "No medium found",
+    [EMEDIUMTYPE] = "Wrong medium type",
+    [ECANCELED] = "Operation canceled",
+    [ENOKEY] = "Required key not available",
+    [EKEYEXPIRED] = "Key has expired",
+    [EKEYREVOKED] = "Key has been revoked",
+    [EKEYREJECTED] = "Key was rejected by service",
+    [EOWNERDEAD] = "Owner died",
+    [ENOTRECOVERABLE] = "State not recoverable",
+    [ERFKILL] = "Operation not possible due to RF-kill",
+    [EHWPOISON] = "Memory page has hardware error",
+};
+
+/* The table spans 0..EHWPOISON exactly: the ABI gaps stay NULL entries. */
+_Static_assert(sizeof errmsg / sizeof errmsg[0] == EHWPOISON + 1,
+               "strerror table must cover every E* value 0..EHWPOISON");
+
+/* Shared storage for the unknown-value path (see the file-top comment). */
+static char errbuf[32];
+
+/*
+ * Write "Unknown error <errnum>" into dst, truncating to cap bytes and always
+ * NUL-terminating when cap > 0. Hand-rolled so this file needs no stdio.
+ */
+static void
+format_unknown(int errnum, char *dst, size_t cap)
+{
+    static const char prefix[] = "Unknown error ";
+    char digits[12]; /* enough for "-2147483648" */
+    size_t ndigits;
+    size_t i;
+    unsigned long mag;
+
+    if (cap == 0)
+    {
+        return;
+    }
+
+    /* Absolute value as unsigned long; INT_MIN negates safely in long. */
+    mag = (unsigned long)(errnum < 0 ? -(long)errnum : errnum);
+
+    /* Digits, least significant first. */
+    ndigits = 0;
+    do
+    {
+        digits[ndigits] = (char)('0' + (int)(mag % 10));
+        ndigits++;
+        mag /= 10;
+    } while (mag != 0);
+
+    i = 0;
+    while (i + 1 < cap && prefix[i] != '\0')
+    {
+        dst[i] = prefix[i];
+        i++;
+    }
+    if (i + 1 < cap && errnum < 0)
+    {
+        dst[i] = '-';
+        i++;
+    }
+    while (i + 1 < cap && ndigits > 0)
+    {
+        ndigits--;
+        dst[i] = digits[ndigits];
+        i++;
+    }
+    dst[i] = '\0';
+}
+
+/*
+ * Return the message for errnum, or NULL when it is unknown (out of table
+ * range or an ABI gap).
+ */
+static const char *
+lookup(int errnum)
+{
+    if (errnum >= 0 && errnum < (int)(sizeof errmsg / sizeof errmsg[0]))
+    {
+        return errmsg[errnum];
+    }
+    return NULL;
+}
+
+char *
+strerror(int errnum)
+{
+    const char *msg;
+
+    msg = lookup(errnum);
+    if (msg == NULL)
+    {
+        format_unknown(errnum, errbuf, sizeof errbuf);
+        msg = errbuf;
+    }
+    return (char *)msg;
+}
+
+#if VLIBC_LEVEL_GE(2)
+/*
+ * XSI strerror_r: copy the message for errnum into buf (truncated to buflen,
+ * always NUL-terminated when buflen > 0) and return 0. Unknown errnum values
+ * produce "Unknown error <errnum>" with the same success return; buf == NULL
+ * with buflen > 0 yields EINVAL; buflen == 0 writes nothing and returns 0.
+ * The GNU char*-returning semantics are deliberately not implemented.
+ */
+int
+strerror_r(int errnum, char *buf, size_t buflen)
+{
+    const char *msg;
+    char unknown[32];
+    size_t i;
+
+    if (buflen == 0)
+    {
+        return 0;
+    }
+    if (buf == NULL)
+    {
+        return EINVAL;
+    }
+
+    msg = lookup(errnum);
+    if (msg == NULL)
+    {
+        format_unknown(errnum, unknown, sizeof unknown);
+        msg = unknown;
+    }
+
+    i = 0;
+    while (i + 1 < buflen && msg[i] != '\0')
+    {
+        buf[i] = msg[i];
+        i++;
+    }
+    buf[i] = '\0';
+    return 0;
+}
+#endif /* VLIBC_LEVEL_GE(2) */

src/internal/errno.h

@@ -8,6 +8,14 @@
  * (TCB), addressed relative to the x86_64 FS thread pointer; there is no
  * process-global errno object and no compiler-managed TLS (`__thread`) here.
  *
+ * The public <errno.h> is the single canonical home for the errno macro, the
+ * __errno_location() declaration, and the E* constant table (1..133, with
+ * EAGAIN/EWOULDBLOCK and EDEADLK/EDEADLOCK aliases and no values 41/58).
+ * This header includes it instead of keeping a second copy, so the public
+ * and internal views of errno can never drift apart. What stays internal-
+ * only here is the errno TCB-slot offset, an ABI constant the public header
+ * must not expose.
+ *
  * The offset of the errno slot inside the TCB is an ABI constant defined
  * below and consumed by the authoritative TCB layout (see the startup todo,
  * which owns the TCB/DTV layout). No other layer may re-derive errno's
@@ -23,163 +31,7 @@
  */
 #define VLIBC_TCB_ERRNO_OFF 8
 
-/*
+/* errno, __errno_location(), and the E* table live in the public header. */
- * Return the address of the calling thread's errno slot.
+#include <errno.h>
- *
- * Requires the thread pointer (FS) to be initialized to a TCB whose first
- * word is the TCB's own address — the startup todo owns that bootstrap and
- * sets it before any code that can touch errno runs. This function itself
- * performs no setup and no other TCB access.
- *
- * The name sits in the implementation-reserved namespace deliberately: it is
- * this libc's private errno accessor, not public API.
- */
-int *
-__errno_location(void); // NOLINT(bugprone-reserved-identifier)
-
-/* The conventional errno lvalue; resolves to the caller's TCB slot. */
-#define errno (*__errno_location())
-
-/*
- * Error numbers: the Linux errno ABI (asm-generic/errno-base.h plus
- * asm-generic/errno.h, which is the table x86_64 uses), transcribed as
- * kernel-ABI facts. These values are fixed and shared with the kernel. The
- * public <errno.h> is owned by a later todo; this internal copy is what
- * internal code and tests compile against.
- */
-
-#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 of func */
-#define ERANGE 34           /* Math result not representable */
-#define EDEADLK 35          /* Resource deadlock would occur */
-#define ENAMETOOLONG 36     /* File name too long */
-#define ENOLCK 37           /* No record locks available */
-#define ENOSYS 38           /* Invalid system call number */
-#define ENOTEMPTY 39        /* Directory not empty */
-#define ELOOP 40            /* Too many symbolic links encountered */
-#define EWOULDBLOCK EAGAIN  /* Operation would block */
-#define ENOMSG 42           /* No message of desired type */
-#define EIDRM 43            /* Identifier removed */
-#define ECHRNG 44           /* Channel number out of range */
-#define EL2NSYNC 45         /* Level 2 not synchronized */
-#define EL3HLT 46           /* Level 3 halted */
-#define EL3RST 47           /* Level 3 reset */
-#define ELNRNG 48           /* Link number out of range */
-#define EUNATCH 49          /* Protocol driver not attached */
-#define ENOCSI 50           /* No CSI structure available */
-#define EL2HLT 51           /* Level 2 halted */
-#define EBADE 52            /* Invalid exchange */
-#define EBADR 53            /* Invalid request descriptor */
-#define EXFULL 54           /* Exchange full */
-#define ENOANO 55           /* No anode */
-#define EBADRQC 56          /* Invalid request code */
-#define EBADSLT 57          /* Invalid slot */
-#define EDEADLOCK EDEADLK   /* File locking deadlock error */
-#define EBFONT 59           /* Bad font file format */
-#define ENOSTR 60           /* Device not a stream */
-#define ENODATA 61          /* No data available */
-#define ETIME 62            /* Timer expired */
-#define ENOSR 63            /* Out of streams resources */
-#define ENONET 64           /* Machine is not on the network */
-#define ENOPKG 65           /* Package not installed */
-#define EREMOTE 66          /* Object is remote */
-#define ENOLINK 67          /* Link has been severed */
-#define EADV 68             /* Advertise error */
-#define ESRMNT 69           /* Srmount error */
-#define ECOMM 70            /* Communication error on send */
-#define EPROTO 71           /* Protocol error */
-#define EMULTIHOP 72        /* Multihop attempted */
-#define EDOTDOT 73          /* RFS specific error */
-#define EBADMSG 74          /* Not a data message */
-#define EOVERFLOW 75        /* Value too large for defined data type */
-#define ENOTUNIQ 76         /* Name not unique on network */
-#define EBADFD 77           /* File descriptor in bad state */
-#define EREMCHG 78          /* Remote address changed */
-#define ELIBACC 79          /* Can not access a needed shared library */
-#define ELIBBAD 80          /* Accessing a corrupted shared library */
-#define ELIBSCN 81          /* .lib section in a.out corrupted */
-#define ELIBMAX 82          /* Attempting to link in too many shared libraries */
-#define ELIBEXEC 83         /* Cannot exec a shared library directly */
-#define EILSEQ 84           /* Illegal byte sequence */
-#define ERESTART 85         /* Interrupted system call should be restarted */
-#define ESTRPIPE 86         /* Streams pipe error */
-#define EUSERS 87           /* Too many users */
-#define ENOTSOCK 88         /* Socket operation on non-socket */
-#define EDESTADDRREQ 89     /* Destination address required */
-#define EMSGSIZE 90         /* Message too long */
-#define EPROTOTYPE 91       /* Protocol wrong type for socket */
-#define ENOPROTOOPT 92      /* Protocol not available */
-#define EPROTONOSUPPORT 93  /* Protocol not supported */
-#define ESOCKTNOSUPPORT 94  /* Socket type not supported */
-#define EOPNOTSUPP 95       /* Operation not supported on transport endpoint */
-#define EPFNOSUPPORT 96     /* Protocol family not supported */
-#define EAFNOSUPPORT 97     /* Address family not supported by protocol */
-#define EADDRINUSE 98       /* Address already in use */
-#define EADDRNOTAVAIL 99    /* Cannot assign requested address */
-#define ENETDOWN 100        /* Network is down */
-#define ENETUNREACH 101     /* Network is unreachable */
-#define ENETRESET 102       /* Network dropped connection because of reset */
-#define ECONNABORTED 103    /* Software caused connection abort */
-#define ECONNRESET 104      /* Connection reset by peer */
-#define ENOBUFS 105         /* No buffer space available */
-#define EISCONN 106         /* Transport endpoint is already connected */
-#define ENOTCONN 107        /* Transport endpoint is not connected */
-#define ESHUTDOWN 108       /* Cannot send after transport endpoint shutdown */
-#define ETOOMANYREFS 109    /* Too many references: cannot splice */
-#define ETIMEDOUT 110       /* Connection timed out */
-#define ECONNREFUSED 111    /* Connection refused */
-#define EHOSTDOWN 112       /* Host is down */
-#define EHOSTUNREACH 113    /* No route to host */
-#define EALREADY 114        /* Operation already in progress */
-#define EINPROGRESS 115     /* Operation now in progress */
-#define ESTALE 116          /* Stale file handle */
-#define EUCLEAN 117         /* Structure needs cleaning */
-#define ENOTNAM 118         /* Not a XENIX named type file */
-#define ENAVAIL 119         /* No XENIX semaphores available */
-#define EISNAM 120          /* Is a named type file */
-#define EREMOTEIO 121       /* Remote I/O error */
-#define EDQUOT 122          /* Quota exceeded */
-#define ENOMEDIUM 123       /* No medium found */
-#define EMEDIUMTYPE 124     /* Wrong medium type */
-#define ECANCELED 125       /* Operation canceled */
-#define ENOKEY 126          /* Required key not available */
-#define EKEYEXPIRED 127     /* Key has expired */
-#define EKEYREVOKED 128     /* Key has been revoked */
-#define EKEYREJECTED 129    /* Key was rejected by service */
-#define EOWNERDEAD 130      /* Owner died */
-#define ENOTRECOVERABLE 131 /* State not recoverable */
-#define ERFKILL 132         /* Operation not possible due to RF-kill */
-#define EHWPOISON 133       /* Memory page has hardware error */
 
 #endif /* VLIBC_INTERNAL_ERRNO_H */

tests/test_strerror.c

@@ -0,0 +1,145 @@
+/*
+ * vlibc — strerror/strerror_r test (todo 2).
+ *
+ * Exercises the public <errno.h> end to end:
+ *
+ *   1. strerror(0) is "Success"; known values return the exact message and
+ *      are non-NULL and distinct; aliases (EWOULDBLOCK/EDEADLOCK) resolve to
+ *      their canonical entries; the last table value (EHWPOISON) is covered.
+ *   2. Unknown errno values never return NULL and never crash: 9999 and the
+ *      ABI-gap value 41 format as "Unknown error <N>", negatives too.
+ *   3. strerror_r (XSI): returns 0 and fills buf with the right text; an
+ *      unknown value still returns 0 with "Unknown error <N>"; truncation
+ *      into a tiny buf stays NUL-terminated; buflen 0 writes nothing; a NULL
+ *      buf with buflen > 0 returns EINVAL.
+ *
+ * The test deliberately never touches errno itself: under the host libc the
+ * TCB slot our errno macro addresses is glibc's private TLS state, and
+ * writing it would corrupt the host (see tests/syscall_test.c). All coverage
+ * here is through the errnum parameters.
+ *
+ * Not part of the library proper; compiled manually for this todo (the
+ * tests/ + make check wiring is owned by a later todo).
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+static int failures;
+
+static void
+check(int cond, const char *what)
+{
+    if (!cond)
+    {
+        printf("FAIL: %s\n", what);
+        failures++;
+    }
+}
+
+/*
+ * Failure scenario (-f): an unknown errno must yield "Unknown error 9999",
+ * non-NULL, without crashing. Prints the observed string; exits 0 only when
+ * the failure behaved exactly as specified.
+ */
+static int
+failure_scenario(void)
+{
+    const char *s = strerror(9999);
+
+    if (s == NULL)
+    {
+        printf("strerror(9999)=NULL\n");
+        return 1;
+    }
+    printf("strerror(9999)=%s\n", s);
+    return strcmp(s, "Unknown error 9999") == 0 ? 0 : 1;
+}
+
+int
+main(int argc, char **argv)
+{
+    const char *a;
+    const char *b;
+    char buf[64];
+    char tiny[8];
+    char untouched[4];
+    int r;
+
+    if (argc == 2 && argv[1][0] == '-' && argv[1][1] == 'f')
+    {
+        return failure_scenario();
+    }
+
+    /* 1. Known values: exact text, non-NULL, distinct. */
+    check(strcmp(strerror(0), "Success") == 0, "strerror(0) == \"Success\"");
+    check(strcmp(strerror(2), "No such file or directory") == 0,
+          "strerror(2) == \"No such file or directory\"");
+    check(strcmp(strerror(EINVAL), "Invalid argument") == 0,
+          "strerror(EINVAL) == \"Invalid argument\"");
+    check(strcmp(strerror(EPERM), "Operation not permitted") == 0,
+          "strerror(EPERM) == \"Operation not permitted\"");
+
+    a = strerror(EINVAL);
+    b = strerror(EPERM);
+    check(a != NULL && b != NULL, "known values non-NULL");
+    check(a != b, "known values distinct");
+
+    /* Aliases resolve to their canonical entries. */
+    check(strerror(EWOULDBLOCK) == strerror(EAGAIN), "EWOULDBLOCK == EAGAIN");
+    check(strerror(EDEADLOCK) == strerror(EDEADLK), "EDEADLOCK == EDEADLK");
+
+    /* Table ends: last defined value and ABI gap values. */
+    check(strerror(EHWPOISON) != NULL, "EHWPOISON (last value) non-NULL");
+    check(strcmp(strerror(41), "Unknown error 41") == 0, "ABI gap 41 unknown");
+    check(strcmp(strerror(58), "Unknown error 58") == 0, "ABI gap 58 unknown");
+
+    /* 2. Unknown values: never NULL, never crash, formatted. */
+    a = strerror(9999);
+    check(a != NULL, "strerror(9999) non-NULL");
+    check(strcmp(a, "Unknown error 9999") == 0, "strerror(9999) text");
+
+    a = strerror(-7);
+    check(a != NULL, "strerror(-7) non-NULL");
+    check(strcmp(a, "Unknown error -7") == 0, "strerror(-7) text");
+
+    /* 3. strerror_r: XSI int return, exact fill. */
+    r = strerror_r(EDOM, buf, sizeof buf);
+    check(r == 0, "strerror_r(EDOM) returns 0");
+    check(strcmp(buf, "Numerical argument out of domain") == 0, "strerror_r(EDOM) fills buf");
+
+    /* Unknown errno still succeeds and formats into buf (XSI). */
+    r = strerror_r(9999, buf, sizeof buf);
+    check(r == 0, "strerror_r(9999) returns 0 (XSI)");
+    check(strcmp(buf, "Unknown error 9999") == 0, "strerror_r(9999) text");
+
+    /* Truncation into a tiny buf stays NUL-terminated. */
+    r = strerror_r(ENAMETOOLONG, tiny, sizeof tiny);
+    check(r == 0, "strerror_r(ENAMETOOLONG, tiny) returns 0");
+    check(tiny[sizeof tiny - 1] == '\0', "tiny buf NUL-terminated");
+    check(strcmp(tiny, "File na") == 0, "tiny buf truncated prefix");
+
+    /* buflen 0: nothing written, still success. */
+    untouched[0] = 'X';
+    untouched[1] = 'X';
+    untouched[2] = 'X';
+    untouched[3] = '\0';
+    r = strerror_r(EDOM, untouched, 0);
+    check(r == 0, "strerror_r(EDOM, buf, 0) returns 0");
+    check(untouched[0] == 'X', "buflen 0 writes nothing");
+
+    /* NULL buf with buflen > 0: EINVAL. */
+    r = strerror_r(EDOM, NULL, 16);
+    check(r == EINVAL, "strerror_r(NULL buf) returns EINVAL");
+
+    if (failures > 0)
+    {
+        printf("FAILED\n");
+    }
+    else
+    {
+        printf("strerror ok\n");
+    }
+    return failures == 0 ? 0 : 1;
+}