commit 4d4d07704ee78221607a18b8118294b0aea1bac4
Author: Sergei Trofimovich <slyfox@gentoo.org>
Date:   Tue Sep 2 00:06:56 2014 +0300

    systools: fix gcc version detecton on non-english locale
    
    Summary:
    ghc runs 'gcc -v' to check if we run under vanilla gcc
    or disaguised clang by checking for string
    
        "gcc version <something>"
    
    But this check does not always work as gcc has that string
    localized via gettext mechanism:
    
        (some gcc's locale strings)
        be.po-msgstr "версія gcc %s\n"
        da.po-msgstr "GCC version %s\n"
        de.po-msgstr "gcc-Version %s %s\n"
        el.po-msgstr "έκδοση gcc %s\n"
        ...
    
    To ping gcc to English locale we now override environment
    variable with 'LANGUAGE=en' value.
    
    Fixes Issue #8825
    
    Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
    
    Test Plan: validate
    
    Reviewers: austin
    
    Reviewed By: austin
    
    Subscribers: simonmar, ezyang, carter
    
    Differential Revision: https://phabricator.haskell.org/D185
    
    GHC Trac Issues: #8825

diff --git a/compiler/main/SysTools.lhs b/compiler/main/SysTools.lhs
index 72fa19b..67926f5 100644
--- a/compiler/main/SysTools.lhs
+++ b/compiler/main/SysTools.lhs
@@ -492,6 +492,51 @@ readCreateProcess proc = do
 
     return (ex, output)
 
+readProcessEnvWithExitCode
+    :: String -- ^ program path
+    -> [String] -- ^ program args
+    -> [(String, String)] -- ^ environment to override
+    -> IO (ExitCode, String, String) -- ^ (exit_code, stdout, stderr)
+readProcessEnvWithExitCode prog args env_update = do
+    current_env <- getEnvironment
+    let new_env = env_update ++ [ (k, v)
+                                | let overriden_keys = map fst env_update
+                                , (k, v) <- current_env
+                                , k `notElem` overriden_keys
+                                ]
+        p       = proc prog args
+
+    (_stdin, Just stdoh, Just stdeh, pid) <-
+        createProcess p{ std_out = CreatePipe
+                       , std_err = CreatePipe
+                       , env     = Just new_env
+                       }
+
+    outMVar <- newEmptyMVar
+    errMVar <- newEmptyMVar
+
+    _ <- forkIO $ do
+        stdo <- hGetContents stdoh
+        _ <- evaluate (length stdo)
+        putMVar outMVar stdo
+
+    _ <- forkIO $ do
+        stde <- hGetContents stdeh
+        _ <- evaluate (length stde)
+        putMVar errMVar stde
+
+    out <- takeMVar outMVar
+    hClose stdoh
+    err <- takeMVar errMVar
+    hClose stdeh
+
+    ex <- waitForProcess pid
+
+    return (ex, out, err)
+
+-- Don't let gcc localize version info string, #8825
+en_locale_env :: [(String, String)]
+en_locale_env = [("LANGUAGE", "en")]
 
 -- If the -B<dir> option is set, add <dir> to PATH.  This works around
 -- a bug in gcc on Windows Vista where it can't find its auxiliary
@@ -746,8 +791,9 @@ getLinkerInfo' dflags = do
                _ -> do
                  -- In practice, we use the compiler as the linker here. Pass
                  -- -Wl,--version to get linker version info.
-                 (exitc, stdo, stde) <- readProcessWithExitCode pgm
-                                        ["-Wl,--version"] ""
+                 (exitc, stdo, stde) <- readProcessEnvWithExitCode pgm
+                                        ["-Wl,--version"]
+                                        en_locale_env
                  -- Split the output by lines to make certain kinds
                  -- of processing easier. In particular, 'clang' and 'gcc'
                  -- have slightly different outputs for '-Wl,--version', but
@@ -802,7 +848,8 @@ getCompilerInfo' dflags = do
 
   -- Process the executable call
   info <- catchIO (do
-                (exitc, stdo, stde) <- readProcessWithExitCode pgm ["-v"] ""
+                (exitc, stdo, stde) <-
+                    readProcessEnvWithExitCode pgm ["-v"] en_locale_env
                 -- Split the output by lines to make certain kinds
                 -- of processing easier.
                 parseCompilerInfo (lines stdo) (lines stde) exitc
@@ -952,7 +999,8 @@ readElfSection _dflags section exe = do
      prog = "readelf"
      args = [Option "-p", Option section, FileOption "" exe]
   --
-  r <- readProcessWithExitCode prog (filter notNull (map showOpt args)) ""
+  r <- readProcessEnvWithExitCode prog (filter notNull (map showOpt args))
+                                  en_locale_env
   case r of
     (ExitSuccess, out, _err) -> return (doFilter (lines out))
     _ -> return Nothing