From a1ff7d8c72a1a659a4624d768930ad803c83aac5 Mon Sep 17 00:00:00 2001
From: morganamilo <morganamilo@archlinux.org>
Date: Tue, 20 May 2025 13:20:45 +0100
Subject: [PATCH] libalpm: set errno and log when setting up temp download dir

Before:
	% pacman -Syy
	:: Synchronising package databases...
	error: failed to synchronize all databases (unexpected error)

After:
	% pacman -Syy
	:: Synchronising package databases...
	error: failed to create temporary download directory /var/lib/pacman/sync/download-P77oXs: Permission denied
	error: failed to synchronize all databases (failed to retrieve some files)
---
 lib/libalpm/util.c | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c
index 8577eb42..058bb77f 100644
--- a/lib/libalpm/util.c
+++ b/lib/libalpm/util.c
@@ -23,6 +23,7 @@
  */
 
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 #include <ctype.h>
 #include <dirent.h>
@@ -959,24 +960,43 @@ char *_alpm_temporary_download_dir_setup(alpm_handle_t *handle, const char *dir)
 	uid_t myuid = getuid();
 	struct passwd const *pw = NULL;
 
-	ASSERT(dir != NULL, return NULL);
+	ASSERT(dir != NULL, RET_ERR(handle, ALPM_ERR_WRONG_ARGS, NULL));
 	if(myuid == 0 && user != NULL) {
-		ASSERT((pw = getpwnam(user)) != NULL, return NULL);
+		errno = 0;
+		pw = getpwnam(user);
+
+		if(pw == NULL) {
+			if(errno == 0) {
+				_alpm_log(handle, ALPM_LOG_ERROR,
+						_("download user '%s' does not exist\n"), user);
+			} else {
+				_alpm_log(handle, ALPM_LOG_ERROR,
+						_("failed to get download user '%s': %s\n"),
+						user, strerror(errno));
+			}
+			RET_ERR(handle, ALPM_ERR_RETRIEVE, NULL);
+		}
 	}
 
 	const char template[] = "download-XXXXXX";
 	size_t newdirlen = strlen(dir) + sizeof(template) + 1;
 	char *newdir = NULL;
-	MALLOC(newdir, newdirlen, return NULL);
+	MALLOC(newdir, newdirlen, RET_ERR(handle, ALPM_ERR_MEMORY, NULL));
 	snprintf(newdir, newdirlen - 1, "%s%s", dir, template);
 	if(mkdtemp(newdir) == NULL) {
+		_alpm_log(handle, ALPM_LOG_ERROR,
+				_("failed to create temporary download directory %s: %s\n"),
+				newdir, strerror(errno));
 		free(newdir);
-		return NULL;
+		RET_ERR(handle, ALPM_ERR_RETRIEVE, NULL);
 	}
 	if(pw != NULL) {
 		if(chown(newdir, pw->pw_uid, pw->pw_gid) == -1) {
+			_alpm_log(handle, ALPM_LOG_ERROR,
+					_("failed to chown temporary download directory %s: %s\n"),
+					newdir, strerror(errno));
 			free(newdir);
-			return NULL;
+			RET_ERR(handle, ALPM_ERR_RETRIEVE, NULL);
 		}
 	}
 	newdir[newdirlen-2] = '/';