Driver: warn on -fPIC/-fpic/-fPIE/-fpie on Windows

Use of these flags would result in the use of ELF-style PIE/PIC code
which is incorrect on Windows.  Windows is inherently PIC by means of
the DLL slide that occurs at load.  This also mirrors the behaviour on
GCC for MinGW.  Currently, the Windows x86_64 forces the relocation
model to PIC (Level 2).  This is unchanged for now, though we should
remove any assumptions on that and change it to a static relocation
model.

llvm-svn: 290533

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 5bab0ef4a8e..8ed12d72b40 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3859,6 +3859,17 @@ ParsePICArgs(const ToolChain &ToolChain, const ArgList &Args) {
                                     options::OPT_fpic, options::OPT_fno_pic,
                                     options::OPT_fPIE, options::OPT_fno_PIE,
                                     options::OPT_fpie, options::OPT_fno_pie);
+  if (Triple.isOSWindows() && LastPICArg &&
+      LastPICArg ==
+          Args.getLastArg(options::OPT_fPIC, options::OPT_fpic,
+                          options::OPT_fPIE, options::OPT_fpie)) {
+    ToolChain.getDriver().Diag(diag::err_drv_unsupported_opt_for_target)
+        << LastPICArg->getSpelling() << Triple.str();
+    if (Triple.getArch() == llvm::Triple::x86_64)
+      return std::make_tuple(llvm::Reloc::PIC_, 2U, false);
+    return std::make_tuple(llvm::Reloc::Static, 0U, false);
+  }
+
   // Check whether the tool chain trumps the PIC-ness decision. If the PIC-ness
   // is forced, then neither PIC nor PIE flags will have no effect.
   if (!ToolChain.isPICDefaultForced()) {