[flang][driver] Introduce FCC_OVERRIDE_OPTIONS. #140556

abidh · 2025-05-19T15:01:20Z

This PR add functionality to change flang command line using environment variable FCC_OVERRIDE_OPTIONS. It is quite similar to what CCC_OVERRIDE_OPTIONS does for clang.

The FCC_OVERRIDE_OPTIONS seemed like the most obvious name to me but I am open to other ideas. The applyOverrideOptions now takes an extra argument that is the name of the environment variable. Previously CCC_OVERRIDE_OPTIONS was hardcoded.

This PR add functionality to change flang command line using environment variable `FCC_OVERRIDE_OPTIONS`. It is quite similar to what `CCC_OVERRIDE_OPTIONS` does for clang. The `FCC_OVERRIDE_OPTIONS` seemed like the most obvious name to me but I am open to other ideas. The `applyOverrideOptions` now takes an extra argument that is the name of the environment variable. Previously `CCC_OVERRIDE_OPTIONS` was hardcoded.

llvmbot · 2025-05-19T15:01:55Z

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

@llvm/pr-subscribers-clang-driver

Author: Abid Qadeer (abidh)

Changes

This PR add functionality to change flang command line using environment variable FCC_OVERRIDE_OPTIONS. It is quite similar to what CCC_OVERRIDE_OPTIONS does for clang.

The FCC_OVERRIDE_OPTIONS seemed like the most obvious name to me but I am open to other ideas. The applyOverrideOptions now takes an extra argument that is the name of the environment variable. Previously CCC_OVERRIDE_OPTIONS was hardcoded.

Full diff: https://github.com/llvm/llvm-project/pull/140556.diff

5 Files Affected:

(modified) clang/include/clang/Driver/Driver.h (+1-1)
(modified) clang/lib/Driver/Driver.cpp (+2-2)
(modified) clang/tools/driver/driver.cpp (+1-1)
(added) flang/test/Driver/fcc_override.f90 (+12)
(modified) flang/tools/flang-driver/driver.cpp (+7)

diff --git a/clang/include/clang/Driver/Driver.h b/clang/include/clang/Driver/Driver.h
index b463dc2a93550..7ca848f11b561 100644
--- a/clang/include/clang/Driver/Driver.h
+++ b/clang/include/clang/Driver/Driver.h
@@ -879,7 +879,7 @@ llvm::Error expandResponseFiles(SmallVectorImpl<const char *> &Args,
 /// See applyOneOverrideOption.
 void applyOverrideOptions(SmallVectorImpl<const char *> &Args,
                           const char *OverrideOpts,
-                          llvm::StringSet<> &SavedStrings,
+                          llvm::StringSet<> &SavedStrings, StringRef EnvVar,
                           raw_ostream *OS = nullptr);
 
 } // end namespace driver
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index a648cc928afdc..a8fea35926a0d 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -7289,7 +7289,7 @@ static void applyOneOverrideOption(raw_ostream &OS,
 void driver::applyOverrideOptions(SmallVectorImpl<const char *> &Args,
                                   const char *OverrideStr,
                                   llvm::StringSet<> &SavedStrings,
-                                  raw_ostream *OS) {
+                                  StringRef EnvVar, raw_ostream *OS) {
   if (!OS)
     OS = &llvm::nulls();
 
@@ -7298,7 +7298,7 @@ void driver::applyOverrideOptions(SmallVectorImpl<const char *> &Args,
     OS = &llvm::nulls();
   }
 
-  *OS << "### CCC_OVERRIDE_OPTIONS: " << OverrideStr << "\n";
+  *OS << "### " << EnvVar << ": " << OverrideStr << "\n";
 
   // This does not need to be efficient.
 
diff --git a/clang/tools/driver/driver.cpp b/clang/tools/driver/driver.cpp
index 82f47ab973064..81964c65c2892 100644
--- a/clang/tools/driver/driver.cpp
+++ b/clang/tools/driver/driver.cpp
@@ -305,7 +305,7 @@ int clang_main(int Argc, char **Argv, const llvm::ToolContext &ToolContext) {
   if (const char *OverrideStr = ::getenv("CCC_OVERRIDE_OPTIONS")) {
     // FIXME: Driver shouldn't take extra initial argument.
     driver::applyOverrideOptions(Args, OverrideStr, SavedStrings,
-                                 &llvm::errs());
+                                 "CCC_OVERRIDE_OPTIONS", &llvm::errs());
   }
 
   std::string Path = GetExecutablePath(ToolContext.Path, CanonicalPrefixes);
diff --git a/flang/test/Driver/fcc_override.f90 b/flang/test/Driver/fcc_override.f90
new file mode 100644
index 0000000000000..55a07803fdde5
--- /dev/null
+++ b/flang/test/Driver/fcc_override.f90
@@ -0,0 +1,12 @@
+! RUN: env FCC_OVERRIDE_OPTIONS="#+-Os +-Oz +-O +-O3 +-Oignore +a +b +c xb Xa Omagic ^-###  " %flang -target x86_64-unknown-linux-gnu %s -O2 b -O3 2>&1 | FileCheck %s
+! RUN: env FCC_OVERRIDE_OPTIONS="x-Werror +-g" %flang -target x86_64-unknown-linux-gnu -Werror %s -c -### 2>&1 | FileCheck %s -check-prefix=RM-WERROR
+
+! CHECK: "-fc1"
+! CHECK-NOT: "-Oignore"
+! CHECK: "-Omagic"
+! CHECK-NOT: "-Oignore"
+
+! RM-WERROR: ### FCC_OVERRIDE_OPTIONS: x-Werror +-g
+! RM-WERROR-NEXT: ### Deleting argument -Werror
+! RM-WERROR-NEXT: ### Adding argument -g at end
+! RM-WERROR-NOT: "-Werror"
diff --git a/flang/tools/flang-driver/driver.cpp b/flang/tools/flang-driver/driver.cpp
index ed52988feaa59..ad0efa3279cef 100644
--- a/flang/tools/flang-driver/driver.cpp
+++ b/flang/tools/flang-driver/driver.cpp
@@ -111,6 +111,13 @@ int main(int argc, const char **argv) {
     }
   }
 
+  llvm::StringSet<> SavedStrings;
+  // Handle FCC_OVERRIDE_OPTIONS, used for editing a command line behind the
+  // scenes.
+  if (const char *OverrideStr = ::getenv("FCC_OVERRIDE_OPTIONS"))
+    clang::driver::applyOverrideOptions(args, OverrideStr, SavedStrings,
+                                        "FCC_OVERRIDE_OPTIONS", &llvm::errs());
+
   // Not in the frontend mode - continue in the compiler driver mode.
 
   // Create DiagnosticsEngine for the compiler driver

tarunprabhu · 2025-05-19T15:21:47Z

The FCC_OVERRIDE_OPTIONS seemed like the most obvious name to me but I am open to other ideas.

Thanks Abid. Perhaps FFC_OVERRIDE_OPTIONS? It has a similar correspondence to CCC_OVERRIDE_OPTIONS as FCFLAGS does to CCFLAGS. But I don't have a strong opinion on this.

kiranchandramohan · 2025-05-28T10:36:18Z

Does CCC_OVERRIDE_OPTIONS expands to Clang Compiler Commandline Override Options? If so FCC_OVERRIDE_OPTIONS expanding to Fortran Compiler Commandline Override Options seems the right replacement.

If CCC_OVERRIDE_OPTIONS expands to Clang C Compiler Override Options then FFC_OVERRIDE_OPTIONS (as suggested by @tarunprabhu) expanding to Flang Fortran Compiler Overrided Options is better.

kiranchandramohan · 2025-05-28T10:55:43Z

flang/test/Driver/fcc_override.f90

@@ -0,0 +1,12 @@
+! RUN: env FCC_OVERRIDE_OPTIONS="#+-Os +-Oz +-O +-O3 +-Oignore +a +b +c xb Xa Omagic ^-###  " %flang -target x86_64-unknown-linux-gnu %s -O2 b -O3 2>&1 | FileCheck %s


Does +, x,X have special meanings? Is that documented anywhere?

I think we should document FCC_OVERRIDE_OPTIONS. One possible location is https://github.com/llvm/llvm-project/blob/main/flang/docs/FlangDriver.md

Yes, those have special meaning and they were only documented in the comments. I have now added documentation for it in the suggested file.

--target=x86_64-unknown-linux-gnu instead of the long deprecated -target

abidh · 2025-05-29T10:10:59Z

Does CCC_OVERRIDE_OPTIONS expands to Clang Compiler Commandline Override Options? If so FCC_OVERRIDE_OPTIONS expanding to Fortran Compiler Commandline Override Options seems the right replacement.

If CCC_OVERRIDE_OPTIONS expands to Clang C Compiler Override Options then FFC_OVERRIDE_OPTIONS (as suggested by @tarunprabhu) expanding to Flang Fortran Compiler Overrided Options is better.

The CCC_OVERRIDE_OPTIONS was introduced in a19fad as replacement of QA_OVERRIDE_GCC3_OPTIONS. I am not sure if there is a definite word on what it actually expands to. I am happy with either of them.

flang/docs/FlangDriver.md

flang/test/Driver/fcc_override.f90

tarunprabhu · 2025-05-29T13:54:40Z

Does CCC_OVERRIDE_OPTIONS expands to Clang Compiler Commandline Override Options? If so FCC_OVERRIDE_OPTIONS expanding to Fortran Compiler Commandline Override Options seems the right replacement.
If CCC_OVERRIDE_OPTIONS expands to Clang C Compiler Override Options then FFC_OVERRIDE_OPTIONS (as suggested by @tarunprabhu) expanding to Flang Fortran Compiler Overrided Options is better.

I am happy with either of them.

Maybe we should split the difference and call it FFF_OVERRIDE_OPTIONS. More Fortran for everyone! :-)

tarunprabhu

Thanks for the changes, Abid. Regarding my suggestions in the documentation, feel free to incorporate or discard them as you see fit.

I'll leave it you and @kiranchandramohan to decide what the name of the environment variable should be.

Other than that, this looks good.

tarunprabhu · 2025-05-30T00:38:38Z

flang/docs/FlangDriver.md

+The environment variable `FCC_OVERRIDE_OPTIONS` can be used to apply a list of
+edits to the input argument lists. The value of this environment variable is
+a space separated list of edits to perform. These edits are applied in order to
+the input argument lists. Edits should be one of the following forms:


What do you think of this?

Suggested change

The environment variable `FCC_OVERRIDE_OPTIONS` can be used to apply a list of

edits to the input argument lists. The value of this environment variable is

a space separated list of edits to perform. These edits are applied in order to

the input argument lists. Edits should be one of the following forms:

The environment variable `FCC_OVERRIDE_OPTIONS` can be used to edit flang's

command line arguments. The value of this variable is a space-separated list of

edits to perform. The edits are applied in the order in which they appear in `FCC_OVERRIDE_OPTIONS`. Each edit should be one of the following forms:

Thanks. This looks better than what I had originally. I have updated the docs.

MaskRay

clang driver code looks good

MaskRay · 2025-05-30T05:33:04Z

flang/test/Driver/fcc_override.f90

@@ -0,0 +1,12 @@
+! RUN: env FCC_OVERRIDE_OPTIONS="#+-Os +-Oz +-O +-O3 +-Oignore +a +b +c xb Xa Omagic ^-###  " %flang -target x86_64-unknown-linux-gnu %s -O2 b -O3 2>&1 | FileCheck %s


--target=x86_64-unknown-linux-gnu instead of the long deprecated -target

kiranchandramohan

LGTM. Thanks.

kiranchandramohan · 2025-05-30T09:52:20Z

flang/tools/flang-driver/driver.cpp

+  llvm::StringSet<> SavedStrings;
+  // Handle FCC_OVERRIDE_OPTIONS, used for editing a command line behind the
+  // scenes.
+  if (const char *OverrideStr = ::getenv("FCC_OVERRIDE_OPTIONS"))


Suggested change

if (const char *OverrideStr = ::getenv("FCC_OVERRIDE_OPTIONS"))

if (const char *overrideStr = ::getenv("FCC_OVERRIDE_OPTIONS"))

kiranchandramohan · 2025-05-30T09:53:17Z

flang/tools/flang-driver/driver.cpp

@@ -111,6 +111,13 @@ int main(int argc, const char **argv) {
    }
  }

+  llvm::StringSet<> SavedStrings;


Suggested change

llvm::StringSet<> SavedStrings;

llvm::StringSet<> savedStrings;

tarunprabhu · 2025-05-30T14:20:01Z

flang/test/Driver/fcc_override.f90

@@ -0,0 +1,17 @@
+! RUN: env FCC_OVERRIDE_OPTIONS="#+-Os +-Oz +-O +-O3 +-Oignore +a +b +c xb Xa Omagic ^-###  " %flang -target x86_64-unknown-linux-gnu %s -O2 b -O3 2>&1 | FileCheck %s


Should this also be --target?

Indeed. Thanks for catching this. Fixed now.

tarunprabhu

Thanks Abid. LGTM.

MaskRay · 2025-05-31T18:39:39Z

flang/docs/FlangDriver.md

+
+- `#`: Silence information about the changes to the command line arguments.
+
+- `^FOO`: Add `FOO` as a new argument at the beginning of the command line.


For clang a.cc, this actually adds FOO after clang. The comment in clang/lib/Driver/Driver.cpp and this description probably should be made more accurate.

I have added "right after the name of the compiler executable" in both places. Hopefully that is enough to make it clear.

MaskRay · 2025-05-31T18:42:28Z

flang/docs/FlangDriver.md

@@ -614,3 +614,30 @@ nvfortran defines `-fast` as
 - `-Mcache_align`: there is no equivalent flag in Flang or Clang.
 - `-Mflushz`: flush-to-zero mode - when `-ffast-math` is specified, Flang will
   link to `crtfastmath.o` to ensure denormal numbers are flushed to zero.
+
+
+## FCC_OVERRIDE_OPTIONS


I noticed that clang/docs doesn't have the documentation. Perhaps we should document clang/docs/UsersManual.rst as well and reference it from FlangDriver.md?

("Each edit should be one of the following forms:" list should probably reference the clang doc)

I will add clang documentation in a separate PR. The FCC_OVERRIDE_OPTIONS one can then probably just refer to it.

abidh · 2025-06-02T11:20:00Z

The test failure in Lower/namelist.f90 was due to CHECK-NOT: bbb while bbb can appeared in compiler generated variable name so unrelated to this change. Opened #142363 to harden that testcase.

As was noted in llvm#140556 (comment), there is no documentation for `CCC_OVERRIDE_OPTIONS`. This adds the missing documentation. The information is duplicate of what we have for `FCC_OVERRIDE_OPTIONS` in flang. Once this goes in and available at https://clang.llvm.org/docs/UsersManual.html then the flang documentation can be changed to refer to it.

As was noted in #140556 (comment), there is no documentation for `CCC_OVERRIDE_OPTIONS`. This adds the missing documentation. The information is duplicate of what we have for `FCC_OVERRIDE_OPTIONS` in flang. Once this goes in and available at https://clang.llvm.org/docs/UsersManual.html then the flang documentation can be changed to refer to it.

As was noted in llvm#140556 (comment), there is no documentation for `CCC_OVERRIDE_OPTIONS`. This adds the missing documentation. The information is duplicate of what we have for `FCC_OVERRIDE_OPTIONS` in flang. Once this goes in and available at https://clang.llvm.org/docs/UsersManual.html then the flang documentation can be changed to refer to it.

As was noted in llvm/llvm-project#140556 (comment), there is no documentation for `CCC_OVERRIDE_OPTIONS`. This adds the missing documentation. The information is duplicate of what we have for `FCC_OVERRIDE_OPTIONS` in flang. Once this goes in and available at https://clang.llvm.org/docs/UsersManual.html then the flang documentation can be changed to refer to it.

As was noted in llvm#140556 (comment), there is no documentation for `CCC_OVERRIDE_OPTIONS`. This adds the missing documentation. The information is duplicate of what we have for `FCC_OVERRIDE_OPTIONS` in flang. Once this goes in and available at https://clang.llvm.org/docs/UsersManual.html then the flang documentation can be changed to refer to it.

This PR add functionality to change `flang` command line using environment variable `FCC_OVERRIDE_OPTIONS`. It is quite similar to what `CCC_OVERRIDE_OPTIONS` does for clang. The `FCC_OVERRIDE_OPTIONS` seemed like the most obvious name to me but I am open to other ideas. The `applyOverrideOptions` now takes an extra argument that is the name of the environment variable. Previously `CCC_OVERRIDE_OPTIONS` was hardcoded.

As was noted in llvm#140556 (comment), there is no documentation for `CCC_OVERRIDE_OPTIONS`. This adds the missing documentation. The information is duplicate of what we have for `FCC_OVERRIDE_OPTIONS` in flang. Once this goes in and available at https://clang.llvm.org/docs/UsersManual.html then the flang documentation can be changed to refer to it.

This PR add functionality to change `flang` command line using environment variable `FCC_OVERRIDE_OPTIONS`. It is quite similar to what `CCC_OVERRIDE_OPTIONS` does for clang. The `FCC_OVERRIDE_OPTIONS` seemed like the most obvious name to me but I am open to other ideas. The `applyOverrideOptions` now takes an extra argument that is the name of the environment variable. Previously `CCC_OVERRIDE_OPTIONS` was hardcoded.

)

abidh requested review from kastiglione, MaskRay, banach-space, tarunprabhu and kiranktp May 19, 2025 15:01

llvmbot added clang Clang issues not falling into any other category clang:driver 'clang' and 'clang++' user-facing binaries. Not 'clang-cl' flang:driver flang Flang issues not falling into any other category labels May 19, 2025

tarunprabhu requested a review from kiranchandramohan May 19, 2025 15:21

kiranchandramohan reviewed May 28, 2025

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Add documentation for FCC_OVERRIDE_OPTIONS.

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abidh added 2 commits May 29, 2025 17:29

Mention that effect on options added by the config files.

d093a6a

Add a test for option from config file.

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tarunprabhu reviewed May 30, 2025

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Handle review comments.

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kiranchandramohan approved these changes May 30, 2025

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Handle review comments.

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Replace -target with --target= to address review comments.

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MaskRay approved these changes May 31, 2025

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Make it clear that ^ adds argument adter compiler name.

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Empty commit to trigger build

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abidh merged commit de38c4e into llvm:main Jun 2, 2025
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abidh mentioned this pull request Jun 2, 2025

[clang][docs] Add docs for CCC_OVERRIDE_OPTIONS. #142396

Merged

searlmc1 pushed a commit to ROCm/llvm-project that referenced this pull request Jun 18, 2025

[flang][driver] Introduce FCC_OVERRIDE_OPTIONS. (llvm#140556) (llvm#2671

37783b6

)

		@@ -0,0 +1,12 @@
		! RUN: env FCC_OVERRIDE_OPTIONS="#+-Os +-Oz +-O +-O3 +-Oignore +a +b +c xb Xa Omagic ^-### " %flang -target x86_64-unknown-linux-gnu %s -O2 b -O3 2>&1 \| FileCheck %s

	if (const char *OverrideStr = ::getenv("FCC_OVERRIDE_OPTIONS"))
	if (const char *overrideStr = ::getenv("FCC_OVERRIDE_OPTIONS"))

	llvm::StringSet<> SavedStrings;
	llvm::StringSet<> savedStrings;

		@@ -0,0 +1,17 @@
		! RUN: env FCC_OVERRIDE_OPTIONS="#+-Os +-Oz +-O +-O3 +-Oignore +a +b +c xb Xa Omagic ^-### " %flang -target x86_64-unknown-linux-gnu %s -O2 b -O3 2>&1 \| FileCheck %s


		- `#`: Silence information about the changes to the command line arguments.

		- `^FOO`: Add `FOO` as a new argument at the beginning of the command line.

[flang][driver] Introduce FCC_OVERRIDE_OPTIONS. #140556

[flang][driver] Introduce FCC_OVERRIDE_OPTIONS. #140556

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