LLONG_MIN example in os.h-Linux

[users/heiko/exim.git] / src / OS / os.h-Linux

diff --git a/src/OS/os.h-Linux b/src/OS/os.h-Linux
index 5186ec89dde44f645efa85bf55ae03954ed24b8a..3fead17d71d24a26c0664957e2eca3c7939bf986 100644 (file)
--- a/src/OS/os.h-Linux
+++ b/src/OS/os.h-Linux
@@ -1,8 +1,8 @@
 /* Exim: OS-specific C header file for Linux */
 
-/* Some weird variants may require invocation with C99 and features.h
-inclusion to build, with the 64-bit arithmetic. Make compiler selection
-their problem, but build anyway. */
+/* Some old systems we've received bug-reports for have a <limits.h> which
+does not pull in <features.h>.  Best to just pull it in now and have done
+with the issue. */
 
 #include <features.h>
 
@@ -57,4 +57,16 @@ extern struct ip_address_item *os_find_running_interfaces_linux(void);
 
 #endif /* __linux__ */
 
+/* Some folks running "unusual" setups with very old libc environments have
+found that _GNU_SOURCE=1 before <features.h> is not sufficient to define some
+constants needed for 64-bit arithmetic.  If you encounter build errors based
+on LLONG_MIN being undefined and various other escape hatches have not helped,
+then change the 0 to 1 in the next block. */
+
+#if 0
+# define LLONG_MIN LONG_LONG_MIN
+# define LLONG_MAX LONG_LONG_MAX
+#endif
+
+
 /* End */