[commit: hsc2hs] master: Add alignment to hsc2hs template (d9c13cb)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/hsc2hs

On branch  : master
Link       : http://git.haskell.org/hsc2hs.git/commitdiff/d9c13cb8f5be89a030783d758fcf7c077351c6a9

>---------------------------------------------------------------

commit d9c13cb8f5be89a030783d758fcf7c077351c6a9
Author: RyanGlScott <ryan.gl.scott at gmail.com>
Date:   Sat Dec 19 01:31:24 2015 +0100

    Add alignment to hsc2hs template
    
    Previously, calculating alignment values was commonly done by defining a
    custom macro via `#let`:
    
    ```
    (y__); }, y__)
    ```
    
    Not only is this tedious, but it also doesn't work in cross-compilation
    mode (see #10272). It makes sense to define this in `hsc2hs` for symmetry
    with `#size`, `#poke`, `#peek`, etc., as well as to make it easier to
    cross-compile `.hsc` files.
    
    Fixes #4340.
    
    Reviewed By: thomie, erikd
    
    Differential Revision: https://phabricator.haskell.org/D1436
    
    GHC Trac Issues: #4340, #10272


>---------------------------------------------------------------

d9c13cb8f5be89a030783d758fcf7c077351c6a9
 CrossCodegen.hs  | 7 +++++++
 DirectCodegen.hs | 2 +-
 template-hsc.h   | 3 +++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/CrossCodegen.hs b/CrossCodegen.hs
index 30bb438..7b26dc7 100644
--- a/CrossCodegen.hs
+++ b/CrossCodegen.hs
@@ -217,6 +217,8 @@ outputSpecial output (z at ZCursor {zCursor=Special pos@(SourcePos file line)  key
        "const" -> outputConst value show
        "offset" -> outputConst ("offsetof(" ++ value ++ ")") (\i -> "(" ++ show i ++ ")")
        "size" -> outputConst ("sizeof(" ++ value ++ ")") (\i -> "(" ++ show i ++ ")")
+       "alignment" -> outputConst (alignment value)
+                                  (\i -> "(" ++ show i ++ ")")
        "peek" -> outputConst ("offsetof(" ++ value ++ ")")
                              (\i -> "(\\hsc_ptr -> peekByteOff hsc_ptr " ++ show i ++ ")")
        "poke" -> outputConst ("offsetof(" ++ value ++ ")")
@@ -281,6 +283,7 @@ outValidityCheck s@(Special pos key value) uniq =
        "const" -> checkValidConst value
        "offset" -> checkValidConst ("offsetof(" ++ value ++ ")")
        "size" -> checkValidConst ("sizeof(" ++ value ++ ")")
+       "alignment" -> checkValidConst (alignment value)
        "peek" -> checkValidConst ("offsetof(" ++ value ++ ")")
        "poke" -> checkValidConst ("offsetof(" ++ value ++ ")")
        "ptr" -> checkValidConst ("offsetof(" ++ value ++ ")")
@@ -439,6 +442,10 @@ stringify = go False . dropWhile isSpace
                     then ' ' : x : go False xs
                     else x : go False xs
 
+-- For #{alignment} codegen; mimic's template-hsc.h's hsc_alignment
+alignment :: String -> String
+alignment t = "offsetof(struct {char x__; " ++ t ++ " (y__); }, y__)"
+
 computeEnum :: ZCursor Token -> TestMonad String
 computeEnum z@(ZCursor (Special _ _ enumText) _ _) =
     case parseEnum enumText of
diff --git a/DirectCodegen.hs b/DirectCodegen.hs
index c6f428d..37564ee 100644
--- a/DirectCodegen.hs
+++ b/DirectCodegen.hs
@@ -54,7 +54,7 @@ outputDirect config outName outDir outBase name toks = do
 
     when (cCrossSafe config) $
         forM_ specials (\ (SourcePos file line,key,_) ->
-            when (not $ key `elem` ["const","offset","size","peek","poke","ptr",
+            when (not $ key `elem` ["const","offset","size","alignment","peek","poke","ptr",
                                     "type","enum","error","warning","include","define","undef",
                                     "if","ifdef","ifndef", "elif","else","endif"]) $
              die (file ++ ":" ++ show line ++ " directive \"" ++ key ++ "\" is not safe for cross-compilation"))
diff --git a/template-hsc.h b/template-hsc.h
index b27faee..edc90c2 100644
--- a/template-hsc.h
+++ b/template-hsc.h
@@ -85,6 +85,9 @@ void *hsc_stdout(void);
 #define hsc_size(t...) \
     hsc_printf("(%ld)", (long) sizeof(t));
 
+#define hsc_alignment(t...) \
+    hsc_printf("(%ld)", (long) offsetof(struct {char x__; t (y__); }, y__));
+
 #define hsc_enum(t, f, print_name, x)                   \
     print_name;                                         \
     hsc_printf (" :: %s\n", #t);                        \