From 1d67b446694e122552b4e7387850e4e9a23d48d3 Mon Sep 17 00:00:00 2001
From: wb2osz <wb2osz@comcast.net>
Date: Wed, 30 Dec 2020 22:32:09 -0500
Subject: [PATCH] Issue 150 - Check whether platform provides strlcpy & strlcat
 or if we need to provide our own.

---
 external/misc/CMakeLists.txt | 31 ++++++++++++++++++++++------
 src/CMakeLists.txt           | 13 ++++++++++++
 src/direwolf.h               | 40 +++++++++++++++---------------------
 3 files changed, 54 insertions(+), 30 deletions(-)

diff --git a/external/misc/CMakeLists.txt b/external/misc/CMakeLists.txt
index 07b10b2..16125d0 100644
--- a/external/misc/CMakeLists.txt
+++ b/external/misc/CMakeLists.txt
@@ -6,12 +6,31 @@ include_directories(
   )
 
 if(LINUX)
-  list(APPEND misc_SOURCES
-    # Provide our own copy of strlcpy and strlcat
-    # because they are not included with Linux.
-    ${CUSTOM_MISC_DIR}/strlcpy.c
-    ${CUSTOM_MISC_DIR}/strlcat.c
-    )
+# Previously -
+#  list(APPEND misc_SOURCES
+#    # Provide our own copy of strlcpy and strlcat
+#    # because they are not included with Linux.
+#    ${CUSTOM_MISC_DIR}/strlcpy.c
+#    ${CUSTOM_MISC_DIR}/strlcat.c
+#    )
+# It seems that Alpine Linux and Void Linux have strlcpy and
+# strlcat so we need to handle the situation more delicately.
+# When doing it this way, there is probably no reason to
+# distinguish between Linux and BSD-like systems here.
+# If we kept going, the same thing could be done for each
+# of the functions and no OS check would be needed.
+
+  if (NOT HAVE_STRLCPY)
+    list(APPEND misc_SOURCES
+      ${CUSTOM_MISC_DIR}/strlcpy.c
+      )
+  endif()
+
+  if (NOT HAVE_STRLCAT)
+    list(APPEND misc_SOURCES
+      ${CUSTOM_MISC_DIR}/strlcat.c
+      )
+  endif()
 
   add_library(misc STATIC
     ${misc_SOURCES}
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 46d3ac7..af747e5 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,3 +1,16 @@
+include(CheckSymbolExists)
+# Some platforms provide their own strlcpy & strlcat. (BSD, MacOSX)
+# Others don't so we provide our own. (Most, but not all Linux)
+# Define the preprocessor macro so libgps does not supply its own version.
+check_symbol_exists(strlcpy string.h HAVE_STRLCPY)
+if(HAVE_STRLCPY)
+    add_compile_options(-DHAVE_STRLCPY)
+endif()
+check_symbol_exists(strlcat string.h HAVE_STRLCAT)
+if(HAVE_STRLCAT)
+    add_compile_options(-DHAVE_STRLCAT)
+endif()
+
 # global includes
 # not ideal but not so slow
 # otherwise use target_include_directories
diff --git a/src/direwolf.h b/src/direwolf.h
index efc329b..b43e5ff 100644
--- a/src/direwolf.h
+++ b/src/direwolf.h
@@ -176,6 +176,7 @@
 #define DW_METERS_TO_FEET(x) ((x) == G_UNKNOWN ? G_UNKNOWN : (x) * 3.2808399)
 #define DW_FEET_TO_METERS(x) ((x) == G_UNKNOWN ? G_UNKNOWN : (x) * 0.3048)
 #define DW_KM_TO_MILES(x) ((x) == G_UNKNOWN ? G_UNKNOWN : (x) * 0.621371192)
+#define DW_MILES_TO_KM(x) ((x) == G_UNKNOWN ? G_UNKNOWN : (x) * 1.609344)
 
 #define DW_KNOTS_TO_MPH(x) ((x) == G_UNKNOWN ? G_UNKNOWN : (x) * 1.15077945)
 #define DW_KNOTS_TO_METERS_PER_SEC(x) ((x) == G_UNKNOWN ? G_UNKNOWN : (x) * 0.51444444444)
@@ -278,43 +279,34 @@ char *strsep(char **stringp, const char *delim);
 char *strtok_r(char *str, const char *delim, char **saveptr);
 #endif
 
-// Don't recall why for everyone.
+// Don't recall why I added this for everyone rather than only for Windows.
 char *strcasestr(const char *S, const char *FIND);
 
 
-#if defined(__OpenBSD__) || defined(__FreeBSD__) || defined(__APPLE__)
+// cmake determines whether strlcpy and strlcat are available
+// or if we need to supply our own.
 
-// strlcpy and strlcat should be in string.h and the C library.
-
-#else   // Use our own copy
-
-
-// These prevent /usr/include/gps.h from providing its own definition.
-#define HAVE_STRLCAT 1
-#define HAVE_STRLCPY 1
-
-
-#define DEBUG_STRL 1
+#define DEBUG_STRL 1	// Extra Debug version when using our own strlcpy, strlcat.
 
+#ifndef HAVE_STRLCPY	// Need to supply our own.
 #if DEBUG_STRL
-
 #define strlcpy(dst,src,siz) strlcpy_debug(dst,src,siz,__FILE__,__func__,__LINE__)
-#define strlcat(dst,src,siz) strlcat_debug(dst,src,siz,__FILE__,__func__,__LINE__)
-
 size_t strlcpy_debug(char *__restrict__ dst, const char *__restrict__ src, size_t siz, const char *file, const char *func, int line);
-size_t strlcat_debug(char *__restrict__ dst, const char *__restrict__ src, size_t siz, const char *file, const char *func, int line);
-
 #else
-
 #define strlcpy(dst,src,siz) strlcpy_debug(dst,src,siz)
-#define strlcat(dst,src,siz) strlcat_debug(dst,src,siz)
-
 size_t strlcpy_debug(char *__restrict__ dst, const char *__restrict__ src, size_t siz);
-size_t strlcat_debug(char *__restrict__ dst, const char *__restrict__ src, size_t siz);
-
 #endif  /* DEBUG_STRL */
+#endif
 
-#endif	/* BSD or Apple */
+#ifndef HAVE_STRLCAT	// Need to supply our own.
+#if DEBUG_STRL
+#define strlcat(dst,src,siz) strlcat_debug(dst,src,siz,__FILE__,__func__,__LINE__)
+size_t strlcat_debug(char *__restrict__ dst, const char *__restrict__ src, size_t siz, const char *file, const char *func, int line);
+#else
+#define strlcat(dst,src,siz) strlcat_debug(dst,src,siz)
+size_t strlcat_debug(char *__restrict__ dst, const char *__restrict__ src, size_t siz);
+#endif  /* DEBUG_STRL */
+#endif
 
 
 #endif   /* ifndef DIREWOLF_H */