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[flang] Align -x language modes with gfortran #130268

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merged 2 commits into from
Mar 12, 2025
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[flang] Align -x language modes with gfortran #130268

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def8ab8
[flang] Remove implicit assumption of fixed-form
inaki-amatria Mar 7, 2025
35ebfdf
[flang] Ensure `-x f95-cpp-input` enables `-cpp`
inaki-amatria Mar 7, 2025
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9 changes: 7 additions & 2 deletions clang/lib/Driver/ToolChains/Flang.cpp
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Expand Up @@ -817,8 +817,13 @@ 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 =
Input.isFilename() &&
llvm::sys::path::extension(Input.getFilename())
.ends_with(types::getTypeTempSuffix(InputType, /*CLStyle=*/false));
if (InputType == types::TY_PP_Fortran && isAtemporaryPreprocessedFile &&
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@DavidTruby DavidTruby Mar 31, 2025 •
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I've only just spotted this, but this requirement that isAtemporaryPreprocessedFile appears to have changed the default for all files to -cpp instead of -nocpp. I don't think this patch intended that change?

E.g. files with the .f90 suffix are now treated as if -cpp were passed, which I don't think is the intended behaviour.

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Sorry I thought it was this part but I actually think it is the other change 😓

!Args.getLastArg(options::OPT_ffixed_form, options::OPT_ffree_form))
CmdArgs.push_back("-ffixed-form");

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6 changes: 6 additions & 0 deletions flang/lib/Frontend/CompilerInvocation.cpp
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Expand Up @@ -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)
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@DavidTruby DavidTruby Mar 31, 2025 •
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I believe we concluded that f95-cpp-input should mean that it has already been preprocessed, and so does not need preprocessing again, and fixed that elsewhere. So this should be PPMacrosFlag::Exclude since -x f95-cpp-input is what we pass for .f90 files, and that's where the issue is coming from.

Edit: Ah, no, we agreed the opposite 😅 , and we are passing the wrong -x for .f90 files. Sorry, I find this all a bit confusing....

.Default(opts.macrosFlag);

opts.noReformat = args.hasArg(clang::driver::options::OPT_fno_reformat);
opts.preprocessIncludeLines =
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35 changes: 35 additions & 0 deletions flang/test/Driver/dash-x-f95-cpp-input.f
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@@ -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 -fsyntax-only -x f95 -cpp %s 2>&1 | FileCheck --check-prefix=SCAN-ERROR %s
! RUN: not %flang -Werror -fsyntax-only -x f95-cpp-input %s 2>&1 | FileCheck --check-prefix=SCAN-ERROR %s

! SCAN-ERROR: error: Could not scan

! RUN: %flang -Werror -fsyntax-only -x f95 -cpp -ffree-form %s 2>&1 | FileCheck --check-prefix=NO-SCAN-ERROR --allow-empty %s
! RUN: %flang -Werror -fsyntax-only -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 -fsyntax-only -x f95 -ffree-form %s 2>&1 | FileCheck --check-prefix=SEMA-ERROR %s
! RUN: not %flang -Werror -fsyntax-only -x f95-cpp-input -nocpp -ffree-form %s 2>&1 | FileCheck --check-prefix=SEMA-ERROR %s

! SEMA-ERROR: error: Semantic errors

! RUN: %flang -Werror -fsyntax-only -x f95 -cpp -ffree-form %s 2>&1 | FileCheck --check-prefix=NO-SEMA-ERROR --allow-empty %s
! RUN: %flang -Werror -fsyntax-only -x f95-cpp-input -ffree-form %s 2>&1 | FileCheck --check-prefix=NO-SEMA-ERROR --allow-empty %s

! NO-SEMA-ERROR-NOT: error
12 changes: 12 additions & 0 deletions flang/test/Driver/dash-x-f95-do-not-assume-fixed-form.f90
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@@ -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 -fsyntax-only -x f95 %s 2>&1 | FileCheck --check-prefix=COMPILE --allow-empty %s
! COMPILE-NOT: error
2 changes: 1 addition & 1 deletion flang/test/Driver/input-from-stdin/input-from-stdin.f90
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Expand Up @@ -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
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