From 98fce1fb43d66f5c74090094be589fe7f859ed20 Mon Sep 17 00:00:00 2001
From: Benny Baumann <BenBE@geshi.org>
Date: Sat, 7 Nov 2020 22:51:46 +0100
Subject: [PATCH] Compatibility function for faccessat

---
 Compat.c                 | 36 ++++++++++++++++++++++++++++++++++++
 Compat.h                 |  5 +++++
 configure.ac             |  2 +-
 linux/LinuxProcessList.c |  1 +
 4 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/Compat.c b/Compat.c
index 096b938a..37e7c042 100644
--- a/Compat.c
+++ b/Compat.c
@@ -9,6 +9,7 @@ in the source distribution for its full text.
 
 #include "Compat.h"
 
+#include <errno.h>
 #include <fcntl.h> // IWYU pragma: keep
 #include <unistd.h>
 #include <sys/stat.h>
@@ -17,6 +18,41 @@ in the source distribution for its full text.
 #include "XUtils.h" // IWYU pragma: keep
 
 
+int Compat_faccessat(int dirfd,
+                     const char* pathname,
+                     int mode,
+                     int flags) {
+   int ret;
+
+#ifdef HAVE_FACCESSAT
+
+   // Implementation note: AT_SYMLINK_NOFOLLOW unsupported on FreeBSD, fallback to lstat in that case
+
+   errno = 0;
+
+   ret = faccessat(dirfd, pathname, mode, flags);
+   if (!ret || errno != EINVAL)
+      return ret;
+
+#endif
+
+   // Error out on unsupported configurations
+   if (dirfd != AT_FDCWD || mode != F_OK) {
+      errno = EINVAL;
+      return -1;
+   }
+
+   // Fallback to stat(2)/lstat(2) depending on flags
+   struct stat statinfo;
+   if(flags) {
+      ret = lstat(pathname, &statinfo);
+   } else {
+      ret = stat(pathname, &statinfo);
+   }
+
+   return ret;
+}
+
 int Compat_fstatat(int dirfd,
                    const char* dirpath,
                    const char* pathname,
diff --git a/Compat.h b/Compat.h
index c0085d5c..e513b1d3 100644
--- a/Compat.h
+++ b/Compat.h
@@ -11,6 +11,11 @@ in the source distribution for its full text.
 #include <sys/stat.h>
 
 
+int Compat_faccessat(int dirfd,
+                     const char* pathname,
+                     int mode,
+                     int flags);
+
 int Compat_fstatat(int dirfd,
                    const char* dirpath,
                    const char* pathname,
diff --git a/configure.ac b/configure.ac
index aed4947e..de47b516 100644
--- a/configure.ac
+++ b/configure.ac
@@ -88,7 +88,7 @@ AC_TYPE_UID_T
 # ----------------------------------------------------------------------
 AC_FUNC_CLOSEDIR_VOID
 AC_FUNC_STAT
-AC_CHECK_FUNCS([fstatat memmove readlinkat strdup strncasecmp strstr])
+AC_CHECK_FUNCS([faccessat fstatat memmove readlinkat strdup strncasecmp strstr])
 
 AC_SEARCH_LIBS([dlopen], [dl dld])
 
diff --git a/linux/LinuxProcessList.c b/linux/LinuxProcessList.c
index 498ee0ef..522b96f5 100644
--- a/linux/LinuxProcessList.c
+++ b/linux/LinuxProcessList.c
@@ -37,6 +37,7 @@ in the source distribution for its full text.
 #endif
 
 #include "CRT.h"
+#include "Compat.h"
 #include "LinuxProcess.h"
 #include "Macros.h"
 #include "Object.h"