3 files changed, 18 insertions, 0 deletions
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 4db6d007fc..1a8c2e834c 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2171,6 +2171,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       D.Diag(diag::warn_drv_clang_unsupported) << A->getAsString(Args);
   }
 
+  if (Args.hasFlag(options::OPT_fapple_pragma_pack,
+                   options::OPT_fno_apple_pragma_pack, false))
+    CmdArgs.push_back("-fapple-pragma-pack");
+
   // Default to -fno-builtin-str{cat,cpy} on Darwin for ARM.
   //
   // FIXME: This is disabled until clang -cc1 supports -fno-builtin-foo. PR4941.
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 79e087e943..34ad608475 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -777,6 +777,8 @@ static void LangOptsToArgs(const LangOptions &Opts,
     Res.push_back("-fdelayed-template-parsing");
   if (Opts.Deprecated)
     Res.push_back("-fdeprecated-macro");
+  if (Opts.ApplePragmaPack)
+    Res.push_back("-fapple-pragma-pack");
 }
 
 static void PreprocessorOptsToArgs(const PreprocessorOptions &Opts,
@@ -1763,6 +1765,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   Opts.FakeAddressSpaceMap = Args.hasArg(OPT_ffake_address_space_map);
   Opts.ParseUnknownAnytype = Args.hasArg(OPT_funknown_anytype);
   Opts.DebuggerSupport = Args.hasArg(OPT_fdebugger_support);
+  Opts.ApplePragmaPack = Args.hasArg(OPT_fapple_pragma_pack);
 
   // Record whether the __DEPRECATED define was requested.
   Opts.Deprecated = Args.hasFlag(OPT_fdeprecated_macro,
diff --git a/lib/Parse/ParsePragma.cpp b/lib/Parse/ParsePragma.cpp
index 2ccb6ea88d..2069d31dd2 100644
--- a/lib/Parse/ParsePragma.cpp
+++ b/lib/Parse/ParsePragma.cpp
@@ -110,6 +110,12 @@ void PragmaPackHandler::HandlePragma(Preprocessor &PP,
       return;
 
     PP.Lex(Tok);
+
+    // In MSVC/gcc, #pragma pack(4) sets the alignment without affecting
+    // the push/pop stack.
+    // In Apple gcc, #pragma pack(4) is equivalent to #pragma pack(push, 4)
+    if (PP.getLangOptions().ApplePragmaPack)
+      Kind = Sema::PPK_Push;
   } else if (Tok.is(tok::identifier)) {
     const IdentifierInfo *II = Tok.getIdentifierInfo();
     if (II->isStr("show")) {
@@ -159,6 +165,11 @@ void PragmaPackHandler::HandlePragma(Preprocessor &PP,
         }
       }
     }
+  } else if (PP.getLangOptions().ApplePragmaPack) {
+    // In MSVC/gcc, #pragma pack() resets the alignment without affecting
+    // the push/pop stack.
+    // In Apple gcc #pragma pack() is equivalent to #pragma pack(pop).
+    Kind = Sema::PPK_Pop;
   }
 
   if (Tok.isNot(tok::r_paren)) {