Add an option to emulate the strange Apple gcc behavior of #pragma pack.

<rdar://problem/10374763>



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@143527 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Basic/LangOptions.def b/include/clang/Basic/LangOptions.def
index 03882f8..5cf40ec 100644
--- a/include/clang/Basic/LangOptions.def
+++ b/include/clang/Basic/LangOptions.def
@@ -150,6 +150,8 @@
 VALUE_LANGOPT(MSCVersion, 32, 0, 
               "version of Microsoft Visual C/C++")
 
+LANGOPT(ApplePragmaPack, 1, 0, "Apple gcc-compatible #pragma pack handling")
+
 #undef LANGOPT
 #undef VALUE_LANGOPT
 #undef BENIGN_LANGOPT
diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index 1a6008e..bfcdc93 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -608,6 +608,8 @@
   HelpText<"Defines the __DEPRECATED macro">;
 def fno_deprecated_macro : Flag<"-fno-deprecated-macro">,
   HelpText<"Undefines the __DEPRECATED macro">;
+def fapple_pragma_pack : Flag<"-fapple-pragma-pack">,
+  HelpText<"Enable Apple gcc-compatible #pragma pack handling">;
 
 //===----------------------------------------------------------------------===//
 // Header Search Options
diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index fea6e4f..40a814e 100644
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -261,6 +261,7 @@
 def faccess_control : Flag<"-faccess-control">, Group<f_Group>;
 def fallow_unsupported : Flag<"-fallow-unsupported">, Group<f_Group>;
 def fapple_kext : Flag<"-fapple-kext">, Group<f_Group>;
+def fapple_pragma_pack : Flag<"-fapple-pragma-pack">, Group<f_Group>;
 def fasm : Flag<"-fasm">, Group<f_Group>;
 
 def fasm_blocks : Flag<"-fasm-blocks">, Group<f_Group>;
@@ -355,6 +356,7 @@
 def fnested_functions : Flag<"-fnested-functions">, Group<f_Group>;
 def fnext_runtime : Flag<"-fnext-runtime">, Group<f_Group>;
 def fno_access_control : Flag<"-fno-access-control">, Group<f_Group>;
+def fno_apple_pragma_pack : Flag<"-fno-apple-pragma-pack">, Group<f_Group>;
 def fno_asm : Flag<"-fno-asm">, Group<f_Group>;
 def fno_asynchronous_unwind_tables : Flag<"-fno-asynchronous-unwind-tables">, Group<f_Group>;
 def fno_assume_sane_operator_new : Flag<"-fno-assume-sane-operator-new">, Group<f_Group>;
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 4db6d00..1a8c2e8 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2171,6 +2171,10 @@
       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 79e087e..34ad608 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -777,6 +777,8 @@
     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 @@
   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 2ccb6ea..2069d31 100644
--- a/lib/Parse/ParsePragma.cpp
+++ b/lib/Parse/ParsePragma.cpp
@@ -110,6 +110,12 @@
       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 @@
         }
       }
     }
+  } 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)) {
diff --git a/test/Sema/pragma-pack-apple.c b/test/Sema/pragma-pack-apple.c
new file mode 100644
index 0000000..5b33c03
--- /dev/null
+++ b/test/Sema/pragma-pack-apple.c
@@ -0,0 +1,10 @@
+// RUN: %clang -fsyntax-only %s 2>&1 | FileCheck %s
+// RUN: %clang -fsyntax-only -fapple-pragma-pack %s 2>&1 | FileCheck -check-prefix=CHECK-APPLE %s
+
+#pragma pack(push,1)
+#pragma pack(2)
+#pragma pack()
+#pragma pack(show)
+
+// CHECK: pack(show) == 8
+// CHECK-APPLE: pack(show) == 1