realise that tgmath.h is a time sink

inc/std.h

@@ -23,7 +23,7 @@
 #include <stdlib.h>
 #include <stdnoreturn.h>
 #include <string.h>
-#include <tgmath.h>
+// #include <tgmath.h>
 #include <threads.h>
 #include <time.h>
 #include <uchar.h>

test/math.c

@@ -1,11 +1,5 @@
 
-#include <stdio.h>
-#include <math.h>
-#include <float.h>
-#include <fenv.h>
-#include <inttypes.h>
-#include <errno.h>
-#include <limits.h>
+#include <std.h>
 
 const char *show_classification(double x) {
     switch(fpclassify(x)) {

todo

@@ -72,6 +72,16 @@ string.h:
 *   strerror_s
 *   strerrorlen_s
 
+tgmath.h:
+*   Due to the use of conditional operator in type-generic macros the
+    expression always expands to the value of type `long double`. This leads
+    to warnings when used with printf, e.g. as in printf("%f\n", exp(0)).
+    Using _Generic macros isn't a good choice either, because it won't work
+    with typedef'd types.
+    In other words there's no pure-C way to do tgmath.h.
+    That's probably the reason msvc stdlib headers don't implement tgmath.h.
+    clang implements it with __attribute__((__overloadable__)).
+
 threads.h:
 *   TODO: add todo items