[Driver] Allow -specs and -nostartfiles to be forwarded to GCC

[pzheng]

Summary

With 6a75496836ea14bcfd2f4b59d35a1cad4ac58cee, these two options are no longer
forwarded to GCC. This patch restores the original behavior.

[MaskRay]

LGTM.

clang/test/Driver/gcc_forward.c

5

Moving nostartfiles before nostdlib to keep an alphabetical order.

Similarly, specs can precede static.

[MaskRay]

Can D83648 be closed now?

BTW, can you describe a bit about your use cases? Forwarding options to gcc does not seem common nowadays...

[pzheng]

In D87162#2257192, @MaskRay wrote:

Can D83648 be closed now?

Yes, I have closed it.

BTW, can you describe a bit about your use cases? Forwarding options to gcc does not seem common nowadays...

It's probably not used very common, but we do have some baremetal use cases still relying on these flags to be propagated to GCC.

clang/test/Driver/gcc_forward.c

5

Thanks for pointing this out. I did not realize the flags are ordered. Will update the patch shortly.

[pzheng]

Updated the test case.

[MaskRay]

LGTM.

It's probably not used very common, but we do have some baremetal use cases still relying on these flags to be propagated to GCC.

Thanks for the explanation! (Though I think in these cases calling ld or ld.lld directly might be better?)

And apologies about the friction but I hope the current behavior is better than the previous whether many unrelated options can be forwarded and many can cause warnings on GCC side.

[pzheng]

In D87162#2257233, @MaskRay wrote:

LGTM.

It's probably not used very common, but we do have some baremetal use cases still relying on these flags to be propagated to GCC.

Thanks for the explanation! (Though I think in these cases calling ld or ld.lld directly might be better?)

And apologies about the friction but I hope the current behavior is better than the previous whether many unrelated options can be forwarded and many can cause warnings on GCC side.

No worries. Hopefully, these flags are the only outliers. Thanks for reviewing the patch!

clang/include/clang/Driver/Options.td

 def nofixprebinding : Flag<["-"], "nofixprebinding">;
 def nolibc : Flag<["-"], "nolibc">;
 def nomultidefs : Flag<["-"], "nomultidefs">;
 def nopie : Flag<["-"], "nopie">;
 def no_pie : Flag<["-"], "no-pie">, Alias<nopie>;
 def noprebind : Flag<["-"], "noprebind">;
 def noprofilelib : Flag<["-"], "noprofilelib">;
 def noseglinkedit : Flag<["-"], "noseglinkedit">;
-def nostartfiles : Flag<["-"], "nostartfiles">;
+def nostartfiles : Flag<["-"], "nostartfiles">, Group<Link_Group>;
 def nostdinc : Flag<["-"], "nostdinc">, Flags<[CoreOption]>;
 def nostdlibinc : Flag<["-"], "nostdlibinc">;
 def nostdincxx : Flag<["-"], "nostdinc++">, Flags<[CC1Option]>,
   HelpText<"Disable standard #include directories for the C++ standard library">;
 def nostdlib : Flag<["-"], "nostdlib">, Group<Link_Group>;
 def nostdlibxx : Flag<["-"], "nostdlib++">;
 def object : Flag<["-"], "object">;
 def o : JoinedOrSeparate<["-"], "o">, Flags<[DriverOption, RenderAsInput, CC1Option, CC1AsOption]>,

 def seglinkedit : Flag<["-"], "seglinkedit">;
 def segprot : MultiArg<["-"], "segprot", 3>;
 def segs__read__only__addr : Separate<["-"], "segs_read_only_addr">;
 def segs__read__write__addr : Separate<["-"], "segs_read_write_addr">;
 def segs__read__ : Joined<["-"], "segs_read_">;
 def shared_libgcc : Flag<["-"], "shared-libgcc">;
 def shared : Flag<["-", "--"], "shared">, Group<Link_Group>;
 def single__module : Flag<["-"], "single_module">;
-def specs_EQ : Joined<["-", "--"], "specs=">;
+def specs_EQ : Joined<["-", "--"], "specs=">, Group<Link_Group>;
 def specs : Separate<["-", "--"], "specs">, Flags<[Unsupported]>;
 def static_libgcc : Flag<["-"], "static-libgcc">;
 def static_libstdcxx : Flag<["-"], "static-libstdc++">;
 def static : Flag<["-", "--"], "static">, Group<Link_Group>, Flags<[NoArgumentUnused]>;
 def std_default_EQ : Joined<["-"], "std-default=">;
 def std_EQ : Joined<["-", "--"], "std=">, Flags<[CC1Option]>,
   Group<CompileOnly_Group>, HelpText<"Language standard to compile for">,
   ValuesCode<[{

clang/test/Driver/gcc_forward.c

 // RUN: %clang -### %s -target aarch64-none-elf \
-// RUN:   --coverage -e _start -fuse-ld=lld --ld-path=ld -nostdlib -r -rdynamic -static -static-pie \
+// RUN:   --coverage -e _start -fuse-ld=lld --ld-path=ld -nostartfiles \
+// RUN:   -nostdlib -r -rdynamic -specs=nosys.specs -static -static-pie \
 // RUN:   2>&1 | FileCheck --check-prefix=FORWARD %s
-// FORWARD: gcc{{[^"]*}}" "--coverage" "-fuse-ld=lld" "--ld-path=ld" "-nostdlib" "-rdynamic" "-static" "-static-pie" "-o" "a.out" "{{.*}}.o" "-e" "_start" "-r"
+// FORWARD: gcc{{[^"]*}}" "--coverage" "-fuse-ld=lld" "--ld-path=ld" "-nostartfiles" "-nostdlib" "-rdynamic" "-specs=nosys.specs" "-static" "-static-pie" "-o" "a.out" "{{.*}}.o" "-e" "_start" "-r"
 
 // Check that we don't try to forward -Xclang or -mlinker-version to GCC.
 // PR12920 -- Check also we may not forward W_Group options to GCC.
 //
 // RUN: %clang -target powerpc-unknown-unknown \
 // RUN:   %s \
 // RUN:   -Wall -Wdocumentation \
 // RUN:   -Xclang foo-bar \