Add option for making foreign calls safe

See achirkin#4

generate/src/Write/Cabal.hs

@@ -56,6 +56,13 @@ writeCabal modules platforms guardInfo =
 
         {vcat $ writePlatformFlag <$> platforms}
 
+        flag safe-foreign-calls
+            description:
+              Do not mark foreign imports as 'unsafe'. This means that
+              callbacks from Vulkan to Haskell will work. If you are using
+              these then make sure this flag is enabled.
+            default: False
+
         library
           hs-source-dirs:      src
           -- We need to use cpphs, as regular cpp ruins latex math with lines
@@ -64,6 +71,9 @@ writeCabal modules platforms guardInfo =
           build-depends:       cpphs
           exposed-modules:     {indent (-2) . vcat . intercalatePrepend "," $ pretty . mName <$> unguardedModules}
 
+          if flag(safe-foreign-calls)
+            cpp-options: -DSAFE_FOREIGN_CALLS
+
           {indent 0 . vcat $ writeGuardedModules <$> guardGroups}
 
           build-depends:       base >= 4.9 && < 5

generate/src/Write/Command.hs

@@ -49,6 +49,10 @@ commandDoc c@Command {..} = do
   (t, (is, es)) <- toHsType (commandType c)
   let d getDoc = [qci|
   {document getDoc (TopLevel cName)}
-  foreign import ccall "{cName}" {cName} :: {t}
+  foreign import ccall
+  #if !defined(SAFE_FOREIGN_CALLS)
+    unsafe
+  #endif
+    "{cName}" {cName} :: {t}
 |]
   pure (d, is, es)

generate/src/Write/Loader.hs

@@ -179,7 +179,11 @@ writeFunction gm domain c@Command{..} = do
       d= [qci|
         {dropVk cName} :: {domain}Cmds -> {t}
         {dropVk cName} deviceCmds = mk{upperCaseName} (p{upperCaseName} deviceCmds)
-        foreign import ccall unsafe "dynamic" mk{upperCaseName}
+        foreign import ccall
+        #if !defined(SAFE_FOREIGN_CALLS)
+          unsafe
+        #endif
+          "dynamic" mk{upperCaseName}
           :: FunPtr {t} -> {t}
       |]
   pure ((d, gm =<< cPlatform), is, es)