From ef2e922f9642f943199138447b29ec53fa63ea68 Mon Sep 17 00:00:00 2001
From: Joel Rosdahl <joel@rosdahl.net>
Date: Sun, 3 Apr 2022 10:50:43 +0200
Subject: [PATCH] fix: Only use /run/user/<UID>/ccache-tmp if writable
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The fix for #984 addressed a problem when /run/user/0 already exists and
ccache is run with fakeroot. However, it didn’t handle the case when
/run/user/0/ccache-tmp already exists, which will happen for instance if
the real root user has run ccache at least once.

Fix this by using access(2) to verify that the ccache-tmp directory is
writable. Note: Can’t just check the mode bits of the directory since
they appear OK since fakeroot fakes the UID.

Fixes #1044.
---
 src/Config.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Config.cpp b/src/Config.cpp
index b6c51db55..a64e2529b 100644
--- a/src/Config.cpp
+++ b/src/Config.cpp
@@ -1039,7 +1039,7 @@ Config::default_temporary_dir(const std::string& cache_dir)
   static const std::string run_user_tmp_dir = [] {
 #ifdef HAVE_GETEUID
     auto dir = FMT("/run/user/{}/ccache-tmp", geteuid());
-    if (Util::create_dir(dir)) {
+    if (Util::create_dir(dir) && access(dir.c_str(), W_OK) == 0) {
       return dir;
     }
 #endif
-- 
2.47.2