Make src/common/exec.c's error logging less ugly.

This code used elog where it really ought to use ereport, mainly so that
it can report a SQLSTATE different from ERRCODE_INTERNAL_ERROR.  There
were some other random deviations from typical error report practice too.

In addition, we can make some cleanups that were impractical six months
ago:

* Use one variadic macro, instead of several with different numbers
of arguments, reducing the temptation to force-fit messages into
particular numbers of arguments;

* Use %m, even in the frontend case, simplifying the code.

Discussion: https://postgr.es/m/6025.1527351693@sss.pgh.pa.us

src/common/exec.c

@@ -25,14 +25,24 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+/*
+ * Hacky solution to allow expressing both frontend and backend error reports
+ * in one macro call.  First argument of log_error is an errcode() call of
+ * some sort (ignored if FRONTEND); the rest are errmsg_internal() arguments,
+ * i.e. message string and any parameters for it.
+ *
+ * Caller must provide the gettext wrapper around the message string, if
+ * appropriate, so that it gets translated in the FRONTEND case; this
+ * motivates using errmsg_internal() not errmsg().  We handle appending a
+ * newline, if needed, inside the macro, so that there's only one translatable
+ * string per call not two.
+ */
 #ifndef FRONTEND
-/* We use only 3- and 4-parameter elog calls in this file, for simplicity */
-/* NOTE: caller must provide gettext call around str! */
-#define log_error(str, param)	elog(LOG, str, param)
-#define log_error4(str, param, arg1)	elog(LOG, str, param, arg1)
+#define log_error(errcodefn, ...) \
+	ereport(LOG, (errcodefn, errmsg_internal(__VA_ARGS__)))
 #else
-#define log_error(str, param)	(fprintf(stderr, str, param), fputc('\n', stderr))
-#define log_error4(str, param, arg1)	(fprintf(stderr, str, param, arg1), fputc('\n', stderr))
+#define log_error(errcodefn, ...) \
+	(fprintf(stderr, __VA_ARGS__), fputc('\n', stderr))
 #endif
 
 #ifdef _MSC_VER
@@ -124,10 +134,8 @@ find_my_exec(const char *argv0, char *retpath)
 
 	if (!getcwd(cwd, MAXPGPATH))
 	{
-		int			save_errno = errno;
-
-		log_error(_("could not identify current directory: %s"),
-				  strerror(save_errno));
+		log_error(errcode_for_file_access(),
+				  _("could not identify current directory: %m"));
 		return -1;
 	}
 
@@ -145,7 +153,8 @@ find_my_exec(const char *argv0, char *retpath)
 		if (validate_exec(retpath) == 0)
 			return resolve_symlinks(retpath);
 
-		log_error(_("invalid binary \"%s\""), retpath);
+		log_error(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				  _("invalid binary \"%s\""), retpath);
 		return -1;
 	}
 
@@ -194,14 +203,16 @@ find_my_exec(const char *argv0, char *retpath)
 				case -1:		/* wasn't even a candidate, keep looking */
 					break;
 				case -2:		/* found but disqualified */
-					log_error(_("could not read binary \"%s\""),
+					log_error(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+							  _("could not read binary \"%s\""),
 							  retpath);
 					break;
 			}
 		} while (*endp);
 	}
 
-	log_error(_("could not find a \"%s\" to execute"), argv0);
+	log_error(errcode(ERRCODE_UNDEFINED_FILE),
+			  _("could not find a \"%s\" to execute"), argv0);
 	return -1;
 }
 
@@ -240,10 +251,8 @@ resolve_symlinks(char *path)
 	 */
 	if (!getcwd(orig_wd, MAXPGPATH))
 	{
-		int			save_errno = errno;
-
-		log_error(_("could not identify current directory: %s"),
-				  strerror(save_errno));
+		log_error(errcode_for_file_access(),
+				  _("could not identify current directory: %m"));
 		return -1;
 	}
 
@@ -258,10 +267,8 @@ resolve_symlinks(char *path)
 			*lsep = '\0';
 			if (chdir(path) == -1)
 			{
-				int			save_errno = errno;
-
-				log_error4(_("could not change directory to \"%s\": %s"),
-						   path, strerror(save_errno));
+				log_error(errcode_for_file_access(),
+						  _("could not change directory to \"%s\": %m"), path);
 				return -1;
 			}
 			fname = lsep + 1;
@@ -273,10 +280,12 @@ resolve_symlinks(char *path)
 			!S_ISLNK(buf.st_mode))
 			break;
 
+		errno = 0;
 		rllen = readlink(fname, link_buf, sizeof(link_buf));
 		if (rllen < 0 || rllen >= sizeof(link_buf))
 		{
-			log_error(_("could not read symbolic link \"%s\""), fname);
+			log_error(errcode_for_file_access(),
+					  _("could not read symbolic link \"%s\": %m"), fname);
 			return -1;
 		}
 		link_buf[rllen] = '\0';
@@ -288,10 +297,8 @@ resolve_symlinks(char *path)
 
 	if (!getcwd(path, MAXPGPATH))
 	{
-		int			save_errno = errno;
-
-		log_error(_("could not identify current directory: %s"),
-				  strerror(save_errno));
+		log_error(errcode_for_file_access(),
+				  _("could not identify current directory: %m"));
 		return -1;
 	}
 	join_path_components(path, path, link_buf);
@@ -299,10 +306,8 @@ resolve_symlinks(char *path)
 
 	if (chdir(orig_wd) == -1)
 	{
-		int			save_errno = errno;
-
-		log_error4(_("could not change directory to \"%s\": %s"),
-				   orig_wd, strerror(save_errno));
+		log_error(errcode_for_file_access(),
+				  _("could not change directory to \"%s\": %m"), orig_wd);
 		return -1;
 	}
 #endif							/* HAVE_READLINK */
@@ -532,20 +537,15 @@ pclose_check(FILE *stream)
 	if (exitstatus == -1)
 	{
 		/* pclose() itself failed, and hopefully set errno */
-		int			save_errno = errno;
-
-		log_error(_("pclose failed: %s"),
-				  strerror(save_errno));
+		log_error(errcode(ERRCODE_SYSTEM_ERROR),
+				  _("pclose failed: %m"));
 	}
 	else
 	{
 		reason = wait_result_to_str(exitstatus);
-		log_error("%s", reason);
-#ifdef FRONTEND
-		free(reason);
-#else
+		log_error(errcode(ERRCODE_SYSTEM_ERROR),
+				  "%s", reason);
 		pfree(reason);
-#endif
 	}
 	return exitstatus;
 }
@@ -666,19 +666,24 @@ AddUserToTokenDacl(HANDLE hToken)
 			ptdd = (TOKEN_DEFAULT_DACL *) LocalAlloc(LPTR, dwSize);
 			if (ptdd == NULL)
 			{
-				log_error("could not allocate %lu bytes of memory", dwSize);
+				log_error(errcode(ERRCODE_OUT_OF_MEMORY),
+						  _("out of memory"));
 				goto cleanup;
 			}
 
 			if (!GetTokenInformation(hToken, tic, (LPVOID) ptdd, dwSize, &dwSize))
 			{
-				log_error("could not get token information: error code %lu", GetLastError());
+				log_error(errcode(ERRCODE_SYSTEM_ERROR),
+						  "could not get token information: error code %lu",
+						  GetLastError());
 				goto cleanup;
 			}
 		}
 		else
 		{
-			log_error("could not get token information buffer size: error code %lu", GetLastError());
+			log_error(errcode(ERRCODE_SYSTEM_ERROR),
+					  "could not get token information buffer size: error code %lu",
+					  GetLastError());
 			goto cleanup;
 		}
 	}
@@ -688,7 +693,9 @@ AddUserToTokenDacl(HANDLE hToken)
 						   (DWORD) sizeof(ACL_SIZE_INFORMATION),
 						   AclSizeInformation))
 	{
-		log_error("could not get ACL information: error code %lu", GetLastError());
+		log_error(errcode(ERRCODE_SYSTEM_ERROR),
+				  "could not get ACL information: error code %lu",
+				  GetLastError());
 		goto cleanup;
 	}
 
@@ -704,13 +711,15 @@ AddUserToTokenDacl(HANDLE hToken)
 	pacl = (PACL) LocalAlloc(LPTR, dwNewAclSize);
 	if (pacl == NULL)
 	{
-		log_error("could not allocate %lu bytes of memory", dwNewAclSize);
+		log_error(errcode(ERRCODE_OUT_OF_MEMORY),
+				  _("out of memory"));
 		goto cleanup;
 	}
 
 	if (!InitializeAcl(pacl, dwNewAclSize, ACL_REVISION))
 	{
-		log_error("could not initialize ACL: error code %lu", GetLastError());
+		log_error(errcode(ERRCODE_SYSTEM_ERROR),
+				  "could not initialize ACL: error code %lu", GetLastError());
 		goto cleanup;
 	}
 
@@ -719,13 +728,15 @@ AddUserToTokenDacl(HANDLE hToken)
 	{
 		if (!GetAce(ptdd->DefaultDacl, i, (LPVOID *) &pace))
 		{
-			log_error("could not get ACE: error code %lu", GetLastError());
+			log_error(errcode(ERRCODE_SYSTEM_ERROR),
+					  "could not get ACE: error code %lu", GetLastError());
 			goto cleanup;
 		}
 
 		if (!AddAce(pacl, ACL_REVISION, MAXDWORD, pace, ((PACE_HEADER) pace)->AceSize))
 		{
-			log_error("could not add ACE: error code %lu", GetLastError());
+			log_error(errcode(ERRCODE_SYSTEM_ERROR),
+					  "could not add ACE: error code %lu", GetLastError());
 			goto cleanup;
 		}
 	}
@@ -733,7 +744,9 @@ AddUserToTokenDacl(HANDLE hToken)
 	/* Add the new ACE for the current user */
 	if (!AddAccessAllowedAceEx(pacl, ACL_REVISION, OBJECT_INHERIT_ACE, GENERIC_ALL, pTokenUser->User.Sid))
 	{
-		log_error("could not add access allowed ACE: error code %lu", GetLastError());
+		log_error(errcode(ERRCODE_SYSTEM_ERROR),
+				  "could not add access allowed ACE: error code %lu",
+				  GetLastError());
 		goto cleanup;
 	}
 
@@ -742,7 +755,9 @@ AddUserToTokenDacl(HANDLE hToken)
 
 	if (!SetTokenInformation(hToken, tic, (LPVOID) &tddNew, dwNewAclSize))
 	{
-		log_error("could not set token information: error code %lu", GetLastError());
+		log_error(errcode(ERRCODE_SYSTEM_ERROR),
+				  "could not set token information: error code %lu",
+				  GetLastError());
 		goto cleanup;
 	}
 
@@ -788,13 +803,16 @@ GetTokenUser(HANDLE hToken, PTOKEN_USER *ppTokenUser)
 
 			if (*ppTokenUser == NULL)
 			{
-				log_error("could not allocate %lu bytes of memory", dwLength);
+				log_error(errcode(ERRCODE_OUT_OF_MEMORY),
+						  _("out of memory"));
 				return FALSE;
 			}
 		}
 		else
 		{
-			log_error("could not get token information buffer size: error code %lu", GetLastError());
+			log_error(errcode(ERRCODE_SYSTEM_ERROR),
+					  "could not get token information buffer size: error code %lu",
+					  GetLastError());
 			return FALSE;
 		}
 	}
@@ -808,7 +826,9 @@ GetTokenUser(HANDLE hToken, PTOKEN_USER *ppTokenUser)
 		LocalFree(*ppTokenUser);
 		*ppTokenUser = NULL;
 
-		log_error("could not get token information: error code %lu", GetLastError());
+		log_error(errcode(ERRCODE_SYSTEM_ERROR),
+				  "could not get token information: error code %lu",
+				  GetLastError());
 		return FALSE;
 	}