glibc 2.38 has strlcpy and strlcat but cmake does not detect it.

CMakeLists.txt

@@ -265,9 +265,33 @@ endif(WIN32 OR CYGWIN)
 # requirements
 
 include(CheckSymbolExists)
+
 # Some platforms provide their own strlcpy & strlcat. (BSD, MacOSX)
-# Others don't so we provide our own. (Most, but not all Linux)
+# Others don't so we provide our own. (Windows, most, but not all Linux)
-# Define the preprocessor macro so libgps does not supply its own version.
+# Here we detect whether these are provided by the OS and set a symbol
+# so that:
+#  (1) libgps does not supply its own version.
+#  (2) we know whether we need to supply our own copy.
+#
+# This was all working fine until these were added to the gnu c library 2.38.
+# References:
+*  - https://www.gnu.org/software/libc/sources.html
+#  - https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=NEWS;hb=HEAD
+#
+# This test is not detecting them for glibc 2.38 resulting in a conflict.
+# Why?  Are they declared in a different file or in some strange way?
+#
+# This is how they are declared in include/string.h:
+#
+#	extern __typeof (strlcpy) __strlcpy;
+#	libc_hidden_proto (__strlcpy)
+#	extern __typeof (strlcat) __strlcat;
+#	libc_hidden_proto (__strlcat)
+#
+# Apparently cmake does not recognize this style.
+# Keep this here for BSD type systems where it behaves as expected.
+# We will need to add a hack in direwolf.h to define these if glibc version >= 2.38.
+
 check_symbol_exists(strlcpy string.h HAVE_STRLCPY)
 if(HAVE_STRLCPY)
     add_compile_options(-DHAVE_STRLCPY)

src/direwolf.h

@@ -278,6 +278,8 @@ typedef pthread_mutex_t dw_mutex_t;
 /* Platform differences for string functions. */
 
 
+// Windows is missing a few which are available on Unix/Linux platforms.
+// We provide our own copies when building on Windows.
 
 #if __WIN32__
 char *strsep(char **stringp, const char *delim);
@@ -285,13 +287,49 @@ char *strtok_r(char *str, const char *delim, char **saveptr);
 #endif
 
 // Don't recall why I added this for everyone rather than only for Windows.
+// Potential problem if some C library declares it a little differently.
 char *strcasestr(const char *S, const char *FIND);
 
 
-// cmake determines whether strlcpy and strlcat are available
+// cmake tries to determine whether strlcpy and strlcat are provided by the C runtime library.
-// or if we need to supply our own.
+//
+//	../CMakeLists.txt:check_symbol_exists(strlcpy string.h HAVE_STRLCPY)
+//
+// It sets HAVE_STRLCPY and HAVE_STRLCAT if the corresponding functions are declared.
+// Unfortunately this does not work right for glibc 2.38 which declares the functions
+// like this:
+//
+//	extern __typeof (strlcpy) __strlcpy;
+//	libc_hidden_proto (__strlcpy)
+//	extern __typeof (strlcat) __strlcat;
+//	libc_hidden_proto (__strlcat)
+//
+// Rather than the normal way found in earlier versions:
+//
+//	extern char *strcpy (char *__restrict __dest, const char *__restrict __src)
+//
+// Perhaps a later version of cmake will recognize this form but the version I'm
+// using does not.
+// So, our work around is to assume these functions are available for glibc >= 2.38.
+//
+// In theory, cmake should be able to find the version of the C runtime library, 
+// but I could not get it to work.  So we have the test here.  We will still build
+// own library with the strl... functions but this does not cause a problem
+// because they have special debug names which will not cause a conflict.
+
+#ifdef __GLIBC__
+#if (__GLIBC__ > 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR__ >= 38))
+// These functions first added in 2.38.
+//#warning "DEBUG - glibc >= 2.38"
+#define HAVE_STRLCPY 1
+#define HAVE_STRLCAT 1
+#else
+//#warning "DEBUG - glibc < 2.38"
+#endif
+#endif
 
 #define DEBUG_STRL 1	// Extra Debug version when using our own strlcpy, strlcat.
+			// Should be ignored if not supplying our own.
 
 #ifndef HAVE_STRLCPY	// Need to supply our own.
 #if DEBUG_STRL