Merge pull request #2908 from apense/patch-7

Updated random functions. Fixes #2907

lib/pure/math.nim

@@ -202,28 +202,52 @@ when not defined(JS):
     ## computes x to power raised of y.
     
   # C procs:
-  proc srand(seed: cint) {.importc: "srand", header: "<stdlib.h>".}
-  proc rand(): cint {.importc: "rand", header: "<stdlib.h>".}
+  when defined(vcc):
+    # The "secure" random, available from Windows XP
+    # https://msdn.microsoft.com/en-us/library/sxtz2fa8.aspx
+    # Present in some variants of MinGW but not enough to justify
+    # `when defined(windows)` yet
+    proc rand_s(val: var cuint) {.importc: "rand_s", header: "<stdlib.h>".}
+    # To behave like the normal version
+    proc rand(): cuint = rand_s(result)
+  else:
+    proc srand(seed: cint) {.importc: "srand", header: "<stdlib.h>".}
+    proc rand(): cint {.importc: "rand", header: "<stdlib.h>".}
   
   when not defined(windows):
     proc srand48(seed: clong) {.importc: "srand48", header: "<stdlib.h>".}
     proc drand48(): float {.importc: "drand48", header: "<stdlib.h>".}
     proc random(max: float): float =
       result = drand48() * max
-  when defined(windows):
-    proc random(max: float): float =
-      # we are hardcodeing this because
-      # importcing macros is extremely problematic
-      # and because the value is publicly documented
-      # on MSDN and very unlikely to change
-      const rand_max = 32767
-      result = (float(rand()) / float(rand_max)) * max
-  proc randomize() =
-    randomize(cast[int](epochTime()))
-
-  proc randomize(seed: int) =
-    srand(cint(seed))
-    when declared(srand48): srand48(seed)
+  else:
+    when defined(vcc): # Windows with Visual C
+      proc random(max: float): float =
+        # we are hardcoding this because
+        # importc-ing macros is extremely problematic
+        # and because the value is publicly documented
+        # on MSDN and very unlikely to change
+        # See https://msdn.microsoft.com/en-us/library/296az74e.aspx
+        const rand_max = 4294967295 # UINT_MAX
+        result = (float(rand()) / float(rand_max)) * max
+      proc randomize() = discard
+      proc randomize(seed: int) = discard
+    else: # Windows with another compiler
+      proc random(max: float): float =
+        # we are hardcoding this because
+        # importc-ing macros is extremely problematic
+        # and because the value is publicly documented
+        # on MSDN and very unlikely to change
+        const rand_max = 32767
+        result = (float(rand()) / float(rand_max)) * max
+  
+  when not defined(vcc): # the above code for vcc uses `discard` instead
+    # this is either not Windows or is Windows without vcc
+    proc randomize() =
+      randomize(cast[int](epochTime()))
+    proc randomize(seed: int) =
+      srand(cint(seed)) # rand_s doesn't use srand
+      when declared(srand48): srand48(seed)
+    
   proc random(max: int): int =
     result = int(rand()) mod max