X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/9d26b8c05f5308b474b560fa2a8a1046e2f5c1b6..dc4dc04e65b8011b9242c47099ab1f87f5143b3e:/src/OS/os.h-Linux

diff --git a/src/OS/os.h-Linux b/src/OS/os.h-Linux
index 5186ec89d..3fead17d7 100644
--- 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 */