[Flang] Fix -frelaxed-c-loc-checks being ignored when using the driver

[ShashwathiNavada]

-frelaxed-c-loc-checks worked correctly when passed directly to -fc1, but was silently ignored when using the driver (e.g., flang -c -frelaxed-c-loc-checks), causing the flag to go unused. This patch fixes it by adding OPT_relaxed_c_loc to the addAllArgs call in Flang.cpp
Also extend the existing test with a driver-mode RUN line to cover this path.

[llvmorg-github-actions]

@llvm/pr-subscribers-flang-driver
@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-flang-semantics

Author: ShashwathiNavada

Changes

-frelaxed-c-loc-checks worked correctly when passed directly to -fc1, but was silently ignored when using the driver (e.g., flang -c -frelaxed-c-loc-checks), causing the flag to go unused. This path fixes it by adding OPT_relaxed_c_loc to the addAllArgs call in Flang.cpp
Also extend the existing test with a driver-mode RUN line to cover this path.

---

Full diff: https://github.com/llvm/llvm-project/pull/200733.diff

2 Files Affected:

• (modified) clang/lib/Driver/ToolChains/Flang.cpp (+2-1)
• (modified) flang/test/Semantics/c_loc01-relaxed.f90 (+1)

diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 892a455167205..8b6e83528fecf 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -261,7 +261,8 @@ void Flang::addCodegenOptions(const ArgList &Args,
        options::OPT_frepack_arrays_contiguity_EQ,
        options::OPT_fstack_repack_arrays, options::OPT_fno_stack_repack_arrays,
        options::OPT_ftime_report, options::OPT_ftime_report_EQ,
-       options::OPT_funroll_loops, options::OPT_fno_unroll_loops});
+       options::OPT_funroll_loops, options::OPT_fno_unroll_loops,
+       options::OPT_relaxed_c_loc});
   if (Args.hasArg(options::OPT_fcoarray))
     CmdArgs.push_back("-fcoarray");
 }
diff --git a/flang/test/Semantics/c_loc01-relaxed.f90 b/flang/test/Semantics/c_loc01-relaxed.f90
index 714d4acd5e06f..bfb036b6c0580 100644
--- a/flang/test/Semantics/c_loc01-relaxed.f90
+++ b/flang/test/Semantics/c_loc01-relaxed.f90
@@ -1,4 +1,5 @@
 ! RUN: %python %S/test_errors.py %s %flang_fc1 -frelaxed-c-loc-checks
+! RUN: %python %S/test_errors.py %s %flang -frelaxed-c-loc-checks
 module m
   use iso_c_binding
   type haslen(L)

[tarunprabhu]

Thanks.

[tarunprabhu]

In general, we should not invoke the driver in the semantics tests because there is a lot of work that the driver does that is unnecessary.

If the issue was that the driver was not passing the option along to fc1, it is better to add a test to flang/test/Driver. For instance, something like this:

RUN: %flang -### -frelaxed-c-loc-checks %s 2>&1 | FileCheck %s
CHECK: "-fc1"
CHECK-SAME: "-frelaxed-c-loc-checks"

[ShashwathiNavada]

Done! Thank you !!

[akuhlens]

LGTM, thanks!

[akuhlens]

@tarunprabhu I was honestly a little confused about what the Flang.cpp code was doing... I sort of thought visibility from Options.td what driving the forwarding of arguments. I have corrected that misunderstanding after digging into this code and the call chain between main and fc1_main a little more, but I notice that a lot of this code is just forwarding arguments from flang to fc1. Would you be open to an RFC to add a AutomaticallyForwarded or Forwarded OptionFlag in clang/Options/Options.td and have a generic loop that forwards any options with this flag?

[tarunprabhu]

LGTM. Thanks for the change.

[tarunprabhu]

@tarunprabhu I was honestly a little confused about what the Flang.cpp code was doing... I sort of thought visibility from Options.td what driving the forwarding of arguments. I have corrected that misunderstanding after digging into this code and the call chain between main and fc1_main a little more, but I notice that a lot of this code is just forwarding arguments from flang to fc1. Would you be open to an RFC to add a AutomaticallyForwarded or Forwarded OptionFlag in clang/Options/Options.td and have a generic loop that forwards any options with this flag?

I think it may be sufficient to just forward any options that have not been claimed, but let me check what clang does here. I can't remember off the top of my head.

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[chandraghale]

Thanks, LG for merge !!