From 499e81bfcdd9379bf4619a7c3ad85ed7f2b1dca5 Mon Sep 17 00:00:00 2001
From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Date: Thu, 28 Jul 2022 10:05:18 +0200
Subject: [PATCH] main.c: fix build with kernel < 4.3

PR_CAP_AMBIENT is only available since kernel 4.3 and
https://github.com/torvalds/linux/commit/58319057b7847667f0c9585b9de0e8932b0fdb08
resulting in the following build failure since version 1.7 and
https://github.com/rfjakob/earlyoom/commit/9edc5cfc9ad794ed59baec5e6ee8d1060456a315:

main.c: In function 'main':
main.c:119:11: error: 'PR_CAP_AMBIENT' undeclared (first use in this function)
     prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0);
           ^

Fixes:
 - http://autobuild.buildroot.org/results/5a0ad7e1f6de3c37e40c37d8f583fc699a457753

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[Upstream status: https://github.com/rfjakob/earlyoom/pull/276]
---
 main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/main.c b/main.c
index c068c7c..99ca9e2 100644
--- a/main.c
+++ b/main.c
@@ -115,11 +115,13 @@ int main(int argc, char* argv[])
         fatal(4, "Could not cd to /proc: %s", strerror(errno));
     }
 
+#ifdef PR_CAP_AMBIENT
     // When systemd starts a daemon with capabilities, it uses ambient
     // capabilities to do so. If not dropped, the capabilities can spread
     // to any child process. This is usually not necessary and its a good
     // idea to drop them if not needed.
     prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0);
+#endif
 
     meminfo_t m = parse_meminfo();
 
-- 
2.35.1