[clang] [flang] [flang] Align `-x` language modes with `gfortran` (PR #130268)
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Fri Mar 7 02:00:33 PST 2025
=?utf-8?q?Iñaki?= Amatria Barral <inaki.amatria at appentra.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/130268 at github.com>
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-flang-driver
@llvm/pr-subscribers-clang-driver
Author: Iñaki Amatria Barral (inaki-amatria)
<details>
<summary>Changes</summary>
This PR addresses some of the issues described in https://github.com/llvm/llvm-project/issues/127617. Key changes:
- Stop assuming fixed-form for `-x f95` unless the input is a `.i` file. This change ensures compatibility with `-save-temps` workflows while preventing unintended fixed-form assumptions.
- Ensure `-x f95-cpp-input` enables `-cpp` by default, aligning Flang's behavior with `gfortran`.
---
Full diff: https://github.com/llvm/llvm-project/pull/130268.diff
5 Files Affected:
- (modified) clang/lib/Driver/ToolChains/Flang.cpp (+6-2)
- (modified) flang/lib/Frontend/CompilerInvocation.cpp (+6)
- (added) flang/test/Driver/dash-x-f95-cpp-input.f (+35)
- (added) flang/test/Driver/dash-x-f95-do-not-assume-fixed-form.f90 (+12)
- (modified) flang/test/Driver/input-from-stdin/input-from-stdin.f90 (+1-1)
``````````diff
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index d4fea633d0edf..f6b23cec9c2ee 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -817,8 +817,12 @@ void Flang::ConstructJob(Compilation &C, const JobAction &JA,
// 'flang -E' always produces output that is suitable for use as fixed form
// Fortran. However it is only valid free form source if the original is also
- // free form.
- if (InputType == types::TY_PP_Fortran &&
+ // free form. Ensure this logic does not incorrectly assume fixed-form for
+ // cases where it shouldn't, such as `flang -x f95 foo.f90`.
+ bool isAtemporaryPreprocessedFile =
+ llvm::sys::path::extension(Input.getFilename())
+ .ends_with(types::getTypeTempSuffix(InputType, /*CLStyle=*/false));
+ if (InputType == types::TY_PP_Fortran && isAtemporaryPreprocessedFile &&
!Args.getLastArg(options::OPT_ffixed_form, options::OPT_ffree_form))
CmdArgs.push_back("-ffixed-form");
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 8b07a50824899..1537122ddced5 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -863,6 +863,12 @@ static void parsePreprocessorArgs(Fortran::frontend::PreprocessorOptions &opts,
(currentArg->getOption().matches(clang::driver::options::OPT_cpp))
? PPMacrosFlag::Include
: PPMacrosFlag::Exclude;
+ // Enable -cpp based on -x unless explicitly disabled with -nocpp
+ if (opts.macrosFlag != PPMacrosFlag::Exclude)
+ if (const auto *dashX = args.getLastArg(clang::driver::options::OPT_x))
+ opts.macrosFlag = llvm::StringSwitch<PPMacrosFlag>(dashX->getValue())
+ .Case("f95-cpp-input", PPMacrosFlag::Include)
+ .Default(opts.macrosFlag);
opts.noReformat = args.hasArg(clang::driver::options::OPT_fno_reformat);
opts.preprocessIncludeLines =
diff --git a/flang/test/Driver/dash-x-f95-cpp-input.f b/flang/test/Driver/dash-x-f95-cpp-input.f
new file mode 100644
index 0000000000000..2f42dc9342842
--- /dev/null
+++ b/flang/test/Driver/dash-x-f95-cpp-input.f
@@ -0,0 +1,35 @@
+program main
+ print *, __FILE__, __LINE__
+end
+
+! This test verifies that `flang`'s `-x` options behave like `gfortran`'s.
+! Specifically:
+! - `-x f95` should process the file based on its extension unless overridden.
+! - `-x f95-cpp-input` should behave like `-x f95` but with preprocessing
+! (`-cpp`) enabled unless overridden.
+
+! ---
+! Ensure the file is treated as fixed-form unless explicitly set otherwise
+! ---
+! RUN: not %flang -Werror -x f95 -cpp %s 2>&1 | FileCheck --check-prefix=SCAN-ERROR %s
+! RUN: not %flang -Werror -x f95-cpp-input %s 2>&1 | FileCheck --check-prefix=SCAN-ERROR %s
+
+! SCAN-ERROR: error
+
+! RUN: %flang -Werror -x f95 -cpp -ffree-form %s 2>&1 | FileCheck --check-prefix=NO-SCAN-ERROR --allow-empty %s
+! RUN: %flang -Werror -x f95-cpp-input -ffree-form %s 2>&1 | FileCheck --check-prefix=NO-SCAN-ERROR --allow-empty %s
+
+! NO-SCAN-ERROR-NOT: error
+
+! ---
+! Ensure `-cpp` is not enabled by default unless explicitly requested
+! ---
+! RUN: not %flang -Werror -x f95 -ffree-form %s 2>&1 | FileCheck --check-prefix=SEMA-ERROR %s
+! RUN: not %flang -Werror -x f95-cpp-input -nocpp -ffree-form %s 2>&1 | FileCheck --check-prefix=SEMA-ERROR %s
+
+! SEMA-ERROR: error
+
+! RUN: %flang -Werror -x f95 -cpp -ffree-form %s 2>&1 | FileCheck --check-prefix=NO-SEMA-ERROR --allow-empty %s
+! RUN: %flang -Werror -x f95-cpp-input -ffree-form %s 2>&1 | FileCheck --check-prefix=NO-SEMA-ERROR --allow-empty %s
+
+! NO-SEMA-ERROR-NOT: error
diff --git a/flang/test/Driver/dash-x-f95-do-not-assume-fixed-form.f90 b/flang/test/Driver/dash-x-f95-do-not-assume-fixed-form.f90
new file mode 100644
index 0000000000000..549286d7f2f3d
--- /dev/null
+++ b/flang/test/Driver/dash-x-f95-do-not-assume-fixed-form.f90
@@ -0,0 +1,12 @@
+! This test verifies that using `-x f95` does not cause the driver to assume
+! this file is in fixed-form.
+
+program main
+ print *, "Hello, World!"
+end
+
+! RUN: %flang -### -x f95 %s 2>&1 | FileCheck --check-prefix=PRINT-PHASES %s
+! PRINT-PHASES-NOT: -ffixed-form
+
+! RUN: %flang -Werror -x f95 %s 2>&1 | FileCheck --check-prefix=COMPILE --allow-empty %s
+! COMPILE-NOT: error
diff --git a/flang/test/Driver/input-from-stdin/input-from-stdin.f90 b/flang/test/Driver/input-from-stdin/input-from-stdin.f90
index 285f0751b35d8..1fcc0340a64ba 100644
--- a/flang/test/Driver/input-from-stdin/input-from-stdin.f90
+++ b/flang/test/Driver/input-from-stdin/input-from-stdin.f90
@@ -6,7 +6,7 @@
! Input type is implicit
! RUN: cat %s | %flang -E -cpp - | FileCheck %s --check-prefix=PP-NOT-DEFINED
! RUN: cat %s | %flang -DNEW -E -cpp - | FileCheck %s --check-prefix=PP-DEFINED
-! RUN: cat %s | %flang -DNEW -E - | FileCheck %s --check-prefix=PP-NOT-DEFINED
+! RUN: cat %s | %flang -DNEW -E - | FileCheck %s --check-prefix=PP-DEFINED
! RUN: cat %s | %flang -DNEW -E -nocpp - | FileCheck %s --check-prefix=PP-NOT-DEFINED
! Input type is explicit
``````````
</details>
https://github.com/llvm/llvm-project/pull/130268
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