Convert elog.c's useful_strerror() into a globally-used strerror wrapper.

elog.c has long had a private strerror wrapper that handles assorted
possible failures or deficiencies of the platform's strerror.  On Windows,
it also knows how to translate Winsock error codes, which the native
strerror does not.  Move all this code into src/port/strerror.c and
define strerror() as a macro that invokes it, so that both our frontend
and backend code will have all of this behavior.

I believe this constitutes an actual bug fix on Windows, since AFAICS
our frontend code did not report Winsock error codes properly before this.
However, the main point is to lay the groundwork for implementing %m
in src/port/snprintf.c: the behavior we want %m to have is this one,
not the native strerror's.

Note that this throws away the prior use of src/port/strerror.c,
which was to implement strerror() on platforms lacking it.  That's
been dead code for nigh twenty years now, since strerror() was
already required by C89.

We should likewise cause strerror_r to use this behavior, but
I'll tackle that separately.

Patch by me, reviewed by Michael Paquier

Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us

1 files changed, 272 insertions, 17 deletions

diff --git a/src/port/strerror.c b/src/port/strerror.c
index e92ebc9f55a..ca6910d2e6c 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -1,30 +1,285 @@
-/* src/port/strerror.c */
-
-/*
- * strerror - map error number to descriptive string
+/*-------------------------------------------------------------------------
+ *
+ * strerror.c
+ *	  Replacement for standard strerror() function
+ *
+ * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
  *
- * This version is obviously somewhat Unix-specific.
+ * IDENTIFICATION
+ *	  src/port/strerror.c
  *
- * based on code by Henry Spencer
- * modified for ANSI by D'Arcy J.M. Cain
+ *-------------------------------------------------------------------------
  */
-
 #include "c.h"
 
+/*
+ * Within this file, "strerror" means the platform's function not pg_strerror
+ */
+#undef strerror
 
-extern const char *const sys_errlist[];
-extern int	sys_nerr;
+static char *get_errno_symbol(int errnum);
+#ifdef WIN32
+static char *win32_socket_strerror(int errnum);
+#endif
 
-const char *
-strerror(int errnum)
+
+/*
+ * A slightly cleaned-up version of strerror()
+ */
+char *
+pg_strerror(int errnum)
 {
-	static char buf[24];
+	/* this buffer is only used if strerror() and get_errno_symbol() fail */
+	static char errorstr_buf[48];
+	char	   *str;
+
+	/* If it's a Windows Winsock error, that needs special handling */
+#ifdef WIN32
+	/* Winsock error code range, per WinError.h */
+	if (errnum >= 10000 && errnum <= 11999)
+		return win32_socket_strerror(errnum);
+#endif
+
+	/* Try the platform's strerror() */
+	str = strerror(errnum);
 
-	if (errnum < 0 || errnum > sys_nerr)
+	/*
+	 * Some strerror()s return an empty string for out-of-range errno.  This
+	 * is ANSI C spec compliant, but not exactly useful.  Also, we may get
+	 * back strings of question marks if libc cannot transcode the message to
+	 * the codeset specified by LC_CTYPE.  If we get nothing useful, first try
+	 * get_errno_symbol(), and if that fails, print the numeric errno.
+	 */
+	if (str == NULL || *str == '\0' || *str == '?')
+		str = get_errno_symbol(errnum);
+
+	if (str == NULL)
 	{
-		sprintf(buf, _("unrecognized error %d"), errnum);
-		return buf;
+		snprintf(errorstr_buf, sizeof(errorstr_buf),
+		/*------
+		  translator: This string will be truncated at 47
+		  characters expanded. */
+				 _("operating system error %d"), errnum);
+		str = errorstr_buf;
 	}
 
-	return sys_errlist[errnum];
+	return str;
 }
+
+/*
+ * Returns a symbol (e.g. "ENOENT") for an errno code.
+ * Returns NULL if the code is unrecognized.
+ */
+static char *
+get_errno_symbol(int errnum)
+{
+	switch (errnum)
+	{
+		case E2BIG:
+			return "E2BIG";
+		case EACCES:
+			return "EACCES";
+#ifdef EADDRINUSE
+		case EADDRINUSE:
+			return "EADDRINUSE";
+#endif
+#ifdef EADDRNOTAVAIL
+		case EADDRNOTAVAIL:
+			return "EADDRNOTAVAIL";
+#endif
+		case EAFNOSUPPORT:
+			return "EAFNOSUPPORT";
+#ifdef EAGAIN
+		case EAGAIN:
+			return "EAGAIN";
+#endif
+#ifdef EALREADY
+		case EALREADY:
+			return "EALREADY";
+#endif
+		case EBADF:
+			return "EBADF";
+#ifdef EBADMSG
+		case EBADMSG:
+			return "EBADMSG";
+#endif
+		case EBUSY:
+			return "EBUSY";
+		case ECHILD:
+			return "ECHILD";
+#ifdef ECONNABORTED
+		case ECONNABORTED:
+			return "ECONNABORTED";
+#endif
+		case ECONNREFUSED:
+			return "ECONNREFUSED";
+#ifdef ECONNRESET
+		case ECONNRESET:
+			return "ECONNRESET";
+#endif
+		case EDEADLK:
+			return "EDEADLK";
+		case EDOM:
+			return "EDOM";
+		case EEXIST:
+			return "EEXIST";
+		case EFAULT:
+			return "EFAULT";
+		case EFBIG:
+			return "EFBIG";
+#ifdef EHOSTUNREACH
+		case EHOSTUNREACH:
+			return "EHOSTUNREACH";
+#endif
+		case EIDRM:
+			return "EIDRM";
+		case EINPROGRESS:
+			return "EINPROGRESS";
+		case EINTR:
+			return "EINTR";
+		case EINVAL:
+			return "EINVAL";
+		case EIO:
+			return "EIO";
+#ifdef EISCONN
+		case EISCONN:
+			return "EISCONN";
+#endif
+		case EISDIR:
+			return "EISDIR";
+#ifdef ELOOP
+		case ELOOP:
+			return "ELOOP";
+#endif
+		case EMFILE:
+			return "EMFILE";
+		case EMLINK:
+			return "EMLINK";
+		case EMSGSIZE:
+			return "EMSGSIZE";
+		case ENAMETOOLONG:
+			return "ENAMETOOLONG";
+		case ENFILE:
+			return "ENFILE";
+		case ENOBUFS:
+			return "ENOBUFS";
+		case ENODEV:
+			return "ENODEV";
+		case ENOENT:
+			return "ENOENT";
+		case ENOEXEC:
+			return "ENOEXEC";
+		case ENOMEM:
+			return "ENOMEM";
+		case ENOSPC:
+			return "ENOSPC";
+		case ENOSYS:
+			return "ENOSYS";
+#ifdef ENOTCONN
+		case ENOTCONN:
+			return "ENOTCONN";
+#endif
+		case ENOTDIR:
+			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
+		case ENOTEMPTY:
+			return "ENOTEMPTY";
+#endif
+#ifdef ENOTSOCK
+		case ENOTSOCK:
+			return "ENOTSOCK";
+#endif
+#ifdef ENOTSUP
+		case ENOTSUP:
+			return "ENOTSUP";
+#endif
+		case ENOTTY:
+			return "ENOTTY";
+		case ENXIO:
+			return "ENXIO";
+#if defined(EOPNOTSUPP) && (!defined(ENOTSUP) || (EOPNOTSUPP != ENOTSUP))
+		case EOPNOTSUPP:
+			return "EOPNOTSUPP";
+#endif
+#ifdef EOVERFLOW
+		case EOVERFLOW:
+			return "EOVERFLOW";
+#endif
+		case EPERM:
+			return "EPERM";
+		case EPIPE:
+			return "EPIPE";
+		case EPROTONOSUPPORT:
+			return "EPROTONOSUPPORT";
+		case ERANGE:
+			return "ERANGE";
+#ifdef EROFS
+		case EROFS:
+			return "EROFS";
+#endif
+		case ESRCH:
+			return "ESRCH";
+#ifdef ETIMEDOUT
+		case ETIMEDOUT:
+			return "ETIMEDOUT";
+#endif
+#ifdef ETXTBSY
+		case ETXTBSY:
+			return "ETXTBSY";
+#endif
+#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
+		case EWOULDBLOCK:
+			return "EWOULDBLOCK";
+#endif
+		case EXDEV:
+			return "EXDEV";
+	}
+
+	return NULL;
+}
+
+
+#ifdef WIN32
+
+/*
+ * Windows' strerror() doesn't know the Winsock codes, so handle them this way
+ */
+static char *
+win32_socket_strerror(int errnum)
+{
+	static char wserrbuf[256];
+	static HANDLE handleDLL = INVALID_HANDLE_VALUE;
+
+	if (handleDLL == INVALID_HANDLE_VALUE)
+	{
+		handleDLL = LoadLibraryEx("netmsg.dll", NULL,
+								  DONT_RESOLVE_DLL_REFERENCES | LOAD_LIBRARY_AS_DATAFILE);
+		if (handleDLL == NULL)
+		{
+			sprintf(wserrbuf, "winsock error %d (could not load netmsg.dll to translate: error code %lu)",
+					errnum, GetLastError());
+			return wserrbuf;
+		}
+	}
+
+	ZeroMemory(&wserrbuf, sizeof(wserrbuf));
+	if (FormatMessage(FORMAT_MESSAGE_IGNORE_INSERTS |
+					  FORMAT_MESSAGE_FROM_SYSTEM |
+					  FORMAT_MESSAGE_FROM_HMODULE,
+					  handleDLL,
+					  errnum,
+					  MAKELANGID(LANG_ENGLISH, SUBLANG_DEFAULT),
+					  wserrbuf,
+					  sizeof(wserrbuf) - 1,
+					  NULL) == 0)
+	{
+		/* Failed to get id */
+		sprintf(wserrbuf, "unrecognized winsock error %d", errnum);
+	}
+
+	return wserrbuf;
+}
+
+#endif							/* WIN32 */