libCom: Recognize hex literals in epicsStrtod()

Allows Windows and VxWorks to accept hex integers as a double.

documentation/RELEASE_NOTES.html

@@ -13,6 +13,14 @@
 
 <!-- Insert new items immediately below here ... -->
 
+<h3>Hex literal support in epicStrtod()</h3>
+
+<p>Some OS implementations of the standard C library routine strtod() do not
+recognize hexadecimal integers, in particular the libraries provided on Windows
+and VxWorks. The internal implementation of epicsStrtod() that these targets use
+now recognizes the 0x prefix and will convert hex numbers correctly. Thanks to
+Dirk Zimoch for suggesting this change.</p>
+
 <h3>Added support for 64-bit Cygwin and MinGW targets</h3>
 
 <p>Both windows-x64-mingw and cygwin-x86_64 build targets are now provided.</p>

src/libCom/misc/epicsStdlib.c

@@ -60,6 +60,12 @@ epicsShareFunc double epicsStrtod(const char *str, char **endp)
         cp++;
     }
 
+    if (epicsStrnCaseCmp("0x", cp, 2) == 0) {
+        if (negative)
+            return strtol(str, endp, 16);
+        else
+            return strtoul(str, endp, 16);
+    }
     if (!isalpha((int)*cp))
         return strtod(str, endp);