From acd44b1f1e59c1b82956239ec22e60fb070e206b Mon Sep 17 00:00:00 2001
From: gitlarryf <larryf@mlinks.net>
Date: Fri, 5 Jan 2024 19:43:03 +0000
Subject: [PATCH] Fix cnex to deal with certain Linux variations on time/clock
 handling.

---
 exec/cnex/CMakeLists.txt   |  7 +++++++
 exec/cnex/lib/time_linux.c | 17 +++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/exec/cnex/CMakeLists.txt b/exec/cnex/CMakeLists.txt
index e869f63e1b..ad25beec05 100644
--- a/exec/cnex/CMakeLists.txt
+++ b/exec/cnex/CMakeLists.txt
@@ -22,6 +22,13 @@ if (${CMAKE_SYSTEM_NAME} STREQUAL "Darwin")
         lib/runtime_posix.c
     )
 elseif (${CMAKE_SYSTEM_NAME} STREQUAL "Linux" OR ${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD" OR ${CMAKE_SYSTEM_NAME} STREQUAL "OpenBSD")
+    # Not all flavors of Linx will have the function clock_gettime(), and some have it in a different include.
+    # See exec/cnex/lib/time_linux.c for more information.
+    include(CheckSymbolExists)
+    check_symbol_exists(clock_gettime "time.h;sys/time.h" HAVE_CLOCK_GETTIME)
+    if(HAVE_CLOCK_GETTIME)
+        add_definitions(-DHAVE_CLOCK_GETTIME)
+    endif()
     set(platform_cnex
         rtl_posix.c
         lib/file_posix.c
diff --git a/exec/cnex/lib/time_linux.c b/exec/cnex/lib/time_linux.c
index fc3cbb5838..94db80bbe0 100644
--- a/exec/cnex/lib/time_linux.c
+++ b/exec/cnex/lib/time_linux.c
@@ -1,6 +1,10 @@
 #define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
+#ifdef HAVE_CLOCK_GETTIME
 #include <time.h>
+#else
+#include <sys/time.h>
+#endif
 
 #include "cell.h"
 #include "exec.h"
@@ -9,17 +13,30 @@
 
 
 static Number NANOSECONDS_PER_SECOND;
+static Number MICROSECONDS_PER_SECOND;
 
 void time_initModule()
 {
     NANOSECONDS_PER_SECOND = number_from_uint64(1000000000LL);
+    MICROSECONDS_PER_SECOND = number_from_uint64(1000000LL);
 }
 
 void time_tick(TExecutor *exec)
 {
+#ifdef HAVE_CLOCK_GETTIME
     struct timespec ts;
 
     clock_gettime(CLOCK_MONOTONIC, &ts);
 
     push(exec->stack, cell_fromNumber(number_add(number_from_uint64(ts.tv_sec), number_divide(number_from_uint64(ts.tv_nsec), NANOSECONDS_PER_SECOND))));
+#else
+    // Not all Linux distros will have clock_gettime(), so we'll resort to gettimeofday() in those cases.  Note the difference between
+    // between timespec and timeval structures as well; where timeval has a tv_usec (Microseconds), vs. tv_nsec (Nanoseconds) member.
+    // This means we have to divide by 1,000,000, not 1,000,000,000, when using timeval and gettimeofday().
+    struct timeval tv;
+
+    gettimeofday(&tv, NULL);
+
+    push(exec->stack, cell_fromNumber(number_add(number_from_uint64(tv.tv_sec), number_divide(number_from_uint64(tv.tv_usec), MICROSECONDS_PER_SECOND))));
+#endif
 }