Split the strsafe strncpy() into its own header file and simplified its usage a bit.

sharedbits/strsafe_impl.h

@@ -3,19 +3,6 @@
 
 #include "start.h"
 
-#ifdef sharedbitsInternalError
-#define sharedbitsprivInternalError sharedbitsInternalError
-#else
-#define sharedbitsprivInternalError sharedbitsPrefixName(InternalError)
-#ifdef sharedbitsStatic
-sharedbitsStatic
-#else
-extern
-#endif
-void sharedbitsprivInternalError(const char *fmt, ...);
-#endif
-
-#ifndef sharedbitsNoVsnprintf
 #ifdef sharedbitsStatic
 sharedbitsStatic
 #endif
@@ -36,33 +23,7 @@ int sharedbitsPrefixName(Vsnprintf)(char *s, size_t n, const char *fmt, va_list
 	return vsnprintf(s, n, fmt, ap);
 #endif
 }
-#endif
-
-#ifdef sharedbitsStatic
-sharedbitsStatic
-#endif
-char *sharedbitsPrefixName(Strncpy)(char *dest, const char *src, size_t n)
-{
-#ifdef _WIN32
-	errno_t err;
-
-	// because strncpy_s() doesn't do this
-	memset(dest, '\0', n * sizeof (char));
-	err = strncpy_s(dest, n, src, _TRUNCATE);
-	if (err != 0 && err != STRUNCATE)
-		// Yes folks, apparently strerror() is unsafe (it's not reentrant, but that's not the point of the MSVC security functions; that's about buffer overflows, and as you'll soon see there really is no need for what the "safe' version is given reentrancy concerns), and not only that, but the replacement, strerror_s(), requires copying and allocation! it's almost like they were TRYING to shove as many error conditions as possible in!
-		// Oh, and you can't just use _sys_errlist[] to bypass this, because even that has a deprecation warning, telling you to use strerror() instead, which in turn sends you back to strerror_s()!
-		// Of course, the fact _sys_errlist[] is a thing and that it's deprecated out of security and not reentrancy shows that the error strings returned by strerror()/strerror_s() are static and unchanging throughout the lifetime of the program, so a truly reentrant strerror_s() would just return the raw const string array directly, or a placeholder like "unknown error" otherwise, but that would be too easy!
-		// And even better, there's no way to get the length of the error message, so you can't even dynamically allocate a large enough buffer if you wanted to!
-		// (Furthermore, cppreference.com says there's strerrorlen_s(), but a) fuck C11, and b) MSDN does not concur.)
-		// So, alas, you'll have to live with just having the error code; sorry.
-		sharedbitsprivInternalError("error calling strncpy_s(): %d", err);
-	return dest;
-#else
-	return strncpy(dest, src, n);
-#endif
-}
-
-#undef sharedbitsprivInternalError
 
 #include "end.h"
+
+#include "strsafe_strncpy_impl.h"

sharedbits/strsafe_strncpy_impl.h

@@ -0,0 +1,47 @@
+// 31 may 2019
+// only requires strsafe_header.h if you don't define sharedbitsStatic as static
+
+#include "start.h"
+
+#ifdef _WIN32
+#ifdef sharedbitsInternalError
+#define sharedbitsprivInternalError sharedbitsInternalError
+#else
+#define sharedbitsprivInternalError sharedbitsPrefixName(InternalError)
+#ifdef sharedbitsStatic
+sharedbitsStatic
+#else
+extern
+#endif
+void sharedbitsprivInternalError(const char *fmt, ...);
+#endif
+#endif
+
+#ifdef sharedbitsStatic
+sharedbitsStatic
+#endif
+char *sharedbitsPrefixName(Strncpy)(char *dest, const char *src, size_t n)
+{
+#ifdef _WIN32
+	errno_t err;
+
+	// because strncpy_s() doesn't do this
+	memset(dest, '\0', n * sizeof (char));
+	err = strncpy_s(dest, n, src, _TRUNCATE);
+	if (err != 0 && err != STRUNCATE)
+		// Yes folks, apparently strerror() is unsafe (it's not reentrant, but that's not the point of the MSVC security functions; that's about buffer overflows, and as you'll soon see there really is no need for what the "safe' version is given reentrancy concerns), and not only that, but the replacement, strerror_s(), requires copying and allocation! it's almost like they were TRYING to shove as many error conditions as possible in!
+		// Oh, and you can't just use _sys_errlist[] to bypass this, because even that has a deprecation warning, telling you to use strerror() instead, which in turn sends you back to strerror_s()!
+		// Of course, the fact _sys_errlist[] is a thing and that it's deprecated out of security and not reentrancy shows that the error strings returned by strerror()/strerror_s() are static and unchanging throughout the lifetime of the program, so a truly reentrant strerror_s() would just return the raw const string array directly, or a placeholder like "unknown error" otherwise, but that would be too easy!
+		// And even better, there's no way to get the length of the error message, so you can't even dynamically allocate a large enough buffer if you wanted to!
+		// (Furthermore, cppreference.com says there's strerrorlen_s(), but a) fuck C11, and b) MSDN does not concur.)
+		// So, alas, you'll have to live with just having the error code; sorry.
+		sharedbitsprivInternalError("error calling strncpy_s(): %d", err);
+	return dest;
+#else
+	return strncpy(dest, src, n);
+#endif
+}
+
+#undef sharedbitsprivInternalError
+
+#include "end.h"

test/noinitwrongthread.c

@@ -23,8 +23,9 @@ static char caseErrorEncodingError[] = "encoding error while handling other case
 
 #define sharedbitsPrefix priv
 #define sharedbitsStatic static
-// do this conditionally to avoid warnings on non-Windows
 #ifdef _WIN32
+// While we do only need strncpy(), our privInternalError() calls vsnprintf(), so include that too.
+#include "../../sharedbits/strsafe_impl.h"
 static void privInternalError(const char *fmt, ...)
 {
 	va_list ap, ap2;
@@ -49,13 +50,7 @@ static void privInternalError(const char *fmt, ...)
 	va_end(ap);
 }
 #else
-#define sharedbitsInternalError
-#define sharedbitsNoVsnprintf
-#endif
-#include "../../sharedbits/strsafe_impl.h"
-#ifndef _WIN32
-#undef sharedbitsNoVsnprintf
-#undef sharedbitsInternalError
+#include "../../sharedbits/strsafe_strncpy_impl.h"
 #endif
 #undef sharedbitsStatic
 #undef sharedbitsPrefix