[clang] [flang] [lld] [flang] Generate main only when a Fortran program statement is present (PR #89938)

[Tom Eccles via cfe-commits]

================
@@ -1191,118 +1191,10 @@ bool tools::addOpenMPRuntime(const Compilation &C, ArgStringList &CmdArgs,
   return true;
 }
 
-/// Determines if --whole-archive is active in the list of arguments.
-static bool isWholeArchivePresent(const ArgList &Args) {
-  bool WholeArchiveActive = false;
-  for (auto *Arg : Args.filtered(options::OPT_Wl_COMMA)) {
-    if (Arg) {
-      for (StringRef ArgValue : Arg->getValues()) {
-        if (ArgValue == "--whole-archive")
-          WholeArchiveActive = true;
-        if (ArgValue == "--no-whole-archive")
-          WholeArchiveActive = false;
-      }
-    }
-  }
-
-  return WholeArchiveActive;
-}
-
-/// Determine if driver is invoked to create a shared object library (-static)
-static bool isSharedLinkage(const ArgList &Args) {
-  return Args.hasArg(options::OPT_shared);
-}
-
-/// Determine if driver is invoked to create a static object library (-shared)
-static bool isStaticLinkage(const ArgList &Args) {
-  return Args.hasArg(options::OPT_static);
-}
-
-/// Add Fortran runtime libs for MSVC
-static void addFortranRuntimeLibsMSVC(const ArgList &Args,
-                                      llvm::opt::ArgStringList &CmdArgs) {
-  unsigned RTOptionID = options::OPT__SLASH_MT;
-  if (auto *rtl = Args.getLastArg(options::OPT_fms_runtime_lib_EQ)) {
-    RTOptionID = llvm::StringSwitch<unsigned>(rtl->getValue())
-                     .Case("static", options::OPT__SLASH_MT)
-                     .Case("static_dbg", options::OPT__SLASH_MTd)
-                     .Case("dll", options::OPT__SLASH_MD)
-                     .Case("dll_dbg", options::OPT__SLASH_MDd)
-                     .Default(options::OPT__SLASH_MT);
-  }
-  switch (RTOptionID) {
-  case options::OPT__SLASH_MT:
-    CmdArgs.push_back("/WHOLEARCHIVE:Fortran_main.static.lib");
-    break;
-  case options::OPT__SLASH_MTd:
-    CmdArgs.push_back("/WHOLEARCHIVE:Fortran_main.static_dbg.lib");
-    break;
-  case options::OPT__SLASH_MD:
-    CmdArgs.push_back("/WHOLEARCHIVE:Fortran_main.dynamic.lib");
-    break;
-  case options::OPT__SLASH_MDd:
-    CmdArgs.push_back("/WHOLEARCHIVE:Fortran_main.dynamic_dbg.lib");
-    break;
-  }
-}
-
-// Add FortranMain runtime lib
-static void addFortranMain(const ToolChain &TC, const ArgList &Args,
-                           llvm::opt::ArgStringList &CmdArgs) {
-  // 0. Shared-library linkage
-  // If we are attempting to link a library, we should not add
-  // -lFortran_main.a to the link line, as the `main` symbol is not
-  // required for a library and should also be provided by one of
-  // the translation units of the code that this shared library
-  // will be linked against eventually.
-  if (isSharedLinkage(Args) || isStaticLinkage(Args)) {
-    return;
-  }
-
-  // 1. MSVC
-  if (TC.getTriple().isKnownWindowsMSVCEnvironment()) {
-    addFortranRuntimeLibsMSVC(Args, CmdArgs);
-    return;
-  }
-
-  // 2. GNU and similar
-  const Driver &D = TC.getDriver();
-  const char *FortranMainLinkFlag = "-lFortran_main";
-
-  // Warn if the user added `-lFortran_main` - this library is an implementation
-  // detail of Flang and should be handled automaticaly by the driver.
-  for (const char *arg : CmdArgs) {
-    if (strncmp(arg, FortranMainLinkFlag, strlen(FortranMainLinkFlag)) == 0)
-      D.Diag(diag::warn_drv_deprecated_custom)
-          << FortranMainLinkFlag
-          << "see the Flang driver documentation for correct usage";
-  }
----------------
tblah wrote:

Removing the Fortran_main library could also break existing builds, but I think it is more reasonable because it was deprecated since the last release.

https://github.com/llvm/llvm-project/pull/89938