P0035R4: add predefined __STDCPP_DEFAULT_NEW_ALIGNMENT__ macro. By default, we

assume that ::operator new provides no more alignment than is necessary for any
primitive type, except when we're on a GNU OS, where glibc's malloc guarantees
to provide 64-bit alignment on 32-bit systems and 128-bit alignment on 64-bit
systems. This can be controlled by the command-line -fnew-alignment flag.

llvm-svn: 282974

1 files changed, 13 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 6b2df349f8b..3406c324645 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1625,6 +1625,8 @@ void CompilerInvocation::setLangDefaults(LangOptions &Opts, InputKind IK,
   Opts.GNUKeywords = Opts.GNUMode;
   Opts.CXXOperatorNames = Opts.CPlusPlus;
 
+  Opts.AlignedAllocation = Opts.CPlusPlus1z;
+
   Opts.DollarIdents = !Opts.AsmPreprocessor;
 }
 
@@ -1937,6 +1939,17 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
     getAllNoBuiltinFuncValues(Args, Opts.NoBuiltinFuncs);
   Opts.NoMathBuiltin = Args.hasArg(OPT_fno_math_builtin);
   Opts.SizedDeallocation = Args.hasArg(OPT_fsized_deallocation);
+  Opts.AlignedAllocation =
+      Args.hasFlag(OPT_faligned_allocation, OPT_fno_aligned_allocation,
+                   Opts.AlignedAllocation);
+  Opts.NewAlignOverride =
+      getLastArgIntValue(Args, OPT_fnew_alignment_EQ, 0, Diags);
+  if (Opts.NewAlignOverride && !llvm::isPowerOf2_32(Opts.NewAlignOverride)) {
+    Arg *A = Args.getLastArg(OPT_fnew_alignment_EQ);
+    Diags.Report(diag::err_fe_invalid_alignment) << A->getAsString(Args)
+                                                 << A->getValue();
+    Opts.NewAlignOverride = 0;
+  }
   Opts.ConceptsTS = Args.hasArg(OPT_fconcepts_ts);
   Opts.HeinousExtensions = Args.hasArg(OPT_fheinous_gnu_extensions);
   Opts.AccessControl = !Args.hasArg(OPT_fno_access_control);