[flang][driver] Do not allow -module-dir to be joined to the value #168748

tarunprabhu · 2025-11-19T18:23:23Z

In f820625, the -module-dir option was modified to allow it to be joined to the argument value, i.e. -module-dir<value> was allowed in addition to -module-dir <value>. While this is consistent with its aliasee, '-J', it is not consistent with the way other long options are handled in flang. This also makes it difficult to add another option such as -module-directives since it is not clear if "ectives" is the name of a directory containing .mod files.

-module-dir<value> is no longer allowed. Only -module-dir <value> may be used. -module-dir=<value> is not allowed either. However, both -J<value> and -J <value> are permitted. -J was made into the "primary" option and -module-dir was made its aliasee instead of the other way around since the former can be both joined and separated while the latter can only be separate.

Fixes #168740

In f820625, the -module-dir option was modified to allow it to be joined to the argument value, i.e. `-module-dir<value>` was allowed in addition to `-module-dir <value>`. While this is consistent with its aliasee, '-J', it is not consistent with the way other long options are handled in flang. This also makes it difficult to add another option such as -module-directives since it is not clear if "ectives" is the name of a directory containing .mod files. `-module-dir<value>` is no longer allowed. Only `-module-dir <value>` may be used. `-module-dir=<value>` is not allowed either. However, both `-J<value>` and `-J <value>` are permitted. `-J` was made into the "primary" option and `-module-dir` was made its aliasee instead of the other way around since the former can be both joined and separated while the latter can only be separate. Fixes llvm#168740

llvmbot · 2025-11-19T18:23:56Z

@llvm/pr-subscribers-clang-driver

Author: Tarun Prabhu (tarunprabhu)

Changes

In f820625, the -module-dir option was modified to allow it to be joined to the argument value, i.e. -module-dir<value> was allowed in addition to -module-dir <value>. While this is consistent with its aliasee, '-J', it is not consistent with the way other long options are handled in flang. This also makes it difficult to add another option such as -module-directives since it is not clear if "ectives" is the name of a directory containing .mod files.

-module-dir<value> is no longer allowed. Only -module-dir <value> may be used. -module-dir=<value> is not allowed either. However, both -J<value> and -J <value> are permitted. -J was made into the "primary" option and -module-dir was made its aliasee instead of the other way around since the former can be both joined and separated while the latter can only be separate.

Fixes #168740

Full diff: https://github.com/llvm/llvm-project/pull/168748.diff

4 Files Affected:

(modified) clang/include/clang/Options/Options.td (+4-6)
(modified) clang/lib/Driver/ToolChains/Flang.cpp (+1-1)
(modified) flang/lib/Frontend/CompilerInvocation.cpp (+1-1)
(modified) flang/test/Driver/write-module.f90 (+14-9)

diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td
index 786acd6abbd21..40a6d0d8c2137 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -7236,11 +7236,14 @@ def cpp : Flag<["-"], "cpp">, Group<f_Group>,
   HelpText<"Enable predefined and command line preprocessor macros">;
 def nocpp : Flag<["-"], "nocpp">, Group<f_Group>,
   HelpText<"Disable predefined and command line preprocessor macros">;
-def module_dir : JoinedOrSeparate<["-"], "module-dir">, MetaVarName<"<dir>">,
+def J : JoinedOrSeparate<["-"], "J">,
+  Flags<[RenderJoined]>,
   HelpText<"Put MODULE files in <dir>">,
   DocBrief<[{This option specifies where to put .mod files for compiled modules.
 It is also added to the list of directories to be searched by an USE statement.
 The default is the current directory.}]>;
+def module_dir : Separate<["-"], "module-dir">, MetaVarName<"<dir>">,
+  Alias<J>;
 
 def ffixed_form : Flag<["-"], "ffixed-form">, Group<f_Group>,
   HelpText<"Process source files in fixed form">;
@@ -7376,11 +7379,6 @@ def fdo_concurrent_to_openmp_EQ : Joined<["-"], "fdo-concurrent-to-openmp=">,
       Values<"none, host, device">;
 } // let Visibility = [FC1Option, FlangOption]
 
-def J : JoinedOrSeparate<["-"], "J">,
-  Flags<[RenderJoined]>, Visibility<[FlangOption, FC1Option]>,
-  Group<gfortran_Group>,
-  Alias<module_dir>;
-
 //===----------------------------------------------------------------------===//
 // FC1 Options
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 270904de544d6..b49cf0f3ce2bb 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -126,7 +126,7 @@ void Flang::addDebugOptions(const llvm::opt::ArgList &Args, const JobAction &JA,
   const auto &TC = getToolChain();
   const Driver &D = TC.getDriver();
   Args.addAllArgs(CmdArgs,
-                  {options::OPT_module_dir, options::OPT_fdebug_module_writer,
+                  {options::OPT_J, options::OPT_fdebug_module_writer,
                    options::OPT_fintrinsic_modules_path, options::OPT_pedantic,
                    options::OPT_std_EQ, options::OPT_W_Joined,
                    options::OPT_fconvert_EQ, options::OPT_fpass_plugin_EQ,
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 893121fe01f27..94cf50747ac65 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -959,7 +959,7 @@ static bool parseSemaArgs(CompilerInvocation &res, llvm::opt::ArgList &args,
 
   // -J/module-dir option
   std::vector<std::string> moduleDirList =
-      args.getAllArgValues(clang::options::OPT_module_dir);
+      args.getAllArgValues(clang::options::OPT_J);
   // User can only specify one -J/-module-dir directory, but may repeat
   // -J/-module-dir as long as the directory is the same each time.
   // https://gcc.gnu.org/onlinedocs/gfortran/Directory-Options.html
diff --git a/flang/test/Driver/write-module.f90 b/flang/test/Driver/write-module.f90
index c4dbaddd4b270..ddced1342f025 100644
--- a/flang/test/Driver/write-module.f90
+++ b/flang/test/Driver/write-module.f90
@@ -3,6 +3,19 @@
 !   * is saved in the _directory specified by the user_
 ! We use `-fsyntax-only` as it stops after the semantic checks (the module file is generated when sema checks are run)
 
+! ------------------------------------------------------------------------------
+! At one time, flang accepted -module-dir<value> (note the lack of a separator
+! between -module-dir and <value>). This is no longer allowed.
+! -module-dir=<value> is also not allowed
+!
+! RUN: not %flang -fsyntax-only -module-dir%t %s 2>&1 \
+! RUN:      | FileCheck %s -check-prefix=JOINED
+!
+! RUN: not %flang -fsyntax-only -module-dir=%t %s 2>&1 \
+! RUN:      | FileCheck %s -check-prefix=JOINED
+!
+! JOINED: error: unknown argument: '-module-dir{{.+}}'
+!
 !--------------------------
 ! -module-dir <value>
 !--------------------------
@@ -10,15 +23,7 @@
 ! RUN: cd %t && %flang -fsyntax-only -module-dir %t/dir-flang %s
 ! RUN: ls %t/dir-flang/testmodule.mod && not ls %t/testmodule.mod
 ! RUN: cd -
-
-!--------------------------
-! -module-dir<value>
-!--------------------------
-! RUN: rm -rf %t && mkdir -p %t/dir-flang
-! RUN: cd %t && %flang -fsyntax-only -module-dir%t/dir-flang %s
-! RUN: ls %t/dir-flang/testmodule.mod && not ls %t/testmodule.mod
-! RUN: cd -
-
+!
 !---------------------------
 ! -J <value>
 !---------------------------

llvmbot · 2025-11-19T18:23:57Z

@llvm/pr-subscribers-flang-driver

Author: Tarun Prabhu (tarunprabhu)

Changes

In f820625, the -module-dir option was modified to allow it to be joined to the argument value, i.e. -module-dir<value> was allowed in addition to -module-dir <value>. While this is consistent with its aliasee, '-J', it is not consistent with the way other long options are handled in flang. This also makes it difficult to add another option such as -module-directives since it is not clear if "ectives" is the name of a directory containing .mod files.

-module-dir<value> is no longer allowed. Only -module-dir <value> may be used. -module-dir=<value> is not allowed either. However, both -J<value> and -J <value> are permitted. -J was made into the "primary" option and -module-dir was made its aliasee instead of the other way around since the former can be both joined and separated while the latter can only be separate.

Fixes #168740

Full diff: https://github.com/llvm/llvm-project/pull/168748.diff

4 Files Affected:

(modified) clang/include/clang/Options/Options.td (+4-6)
(modified) clang/lib/Driver/ToolChains/Flang.cpp (+1-1)
(modified) flang/lib/Frontend/CompilerInvocation.cpp (+1-1)
(modified) flang/test/Driver/write-module.f90 (+14-9)

diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td
index 786acd6abbd21..40a6d0d8c2137 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -7236,11 +7236,14 @@ def cpp : Flag<["-"], "cpp">, Group<f_Group>,
   HelpText<"Enable predefined and command line preprocessor macros">;
 def nocpp : Flag<["-"], "nocpp">, Group<f_Group>,
   HelpText<"Disable predefined and command line preprocessor macros">;
-def module_dir : JoinedOrSeparate<["-"], "module-dir">, MetaVarName<"<dir>">,
+def J : JoinedOrSeparate<["-"], "J">,
+  Flags<[RenderJoined]>,
   HelpText<"Put MODULE files in <dir>">,
   DocBrief<[{This option specifies where to put .mod files for compiled modules.
 It is also added to the list of directories to be searched by an USE statement.
 The default is the current directory.}]>;
+def module_dir : Separate<["-"], "module-dir">, MetaVarName<"<dir>">,
+  Alias<J>;
 
 def ffixed_form : Flag<["-"], "ffixed-form">, Group<f_Group>,
   HelpText<"Process source files in fixed form">;
@@ -7376,11 +7379,6 @@ def fdo_concurrent_to_openmp_EQ : Joined<["-"], "fdo-concurrent-to-openmp=">,
       Values<"none, host, device">;
 } // let Visibility = [FC1Option, FlangOption]
 
-def J : JoinedOrSeparate<["-"], "J">,
-  Flags<[RenderJoined]>, Visibility<[FlangOption, FC1Option]>,
-  Group<gfortran_Group>,
-  Alias<module_dir>;
-
 //===----------------------------------------------------------------------===//
 // FC1 Options
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 270904de544d6..b49cf0f3ce2bb 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -126,7 +126,7 @@ void Flang::addDebugOptions(const llvm::opt::ArgList &Args, const JobAction &JA,
   const auto &TC = getToolChain();
   const Driver &D = TC.getDriver();
   Args.addAllArgs(CmdArgs,
-                  {options::OPT_module_dir, options::OPT_fdebug_module_writer,
+                  {options::OPT_J, options::OPT_fdebug_module_writer,
                    options::OPT_fintrinsic_modules_path, options::OPT_pedantic,
                    options::OPT_std_EQ, options::OPT_W_Joined,
                    options::OPT_fconvert_EQ, options::OPT_fpass_plugin_EQ,
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 893121fe01f27..94cf50747ac65 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -959,7 +959,7 @@ static bool parseSemaArgs(CompilerInvocation &res, llvm::opt::ArgList &args,
 
   // -J/module-dir option
   std::vector<std::string> moduleDirList =
-      args.getAllArgValues(clang::options::OPT_module_dir);
+      args.getAllArgValues(clang::options::OPT_J);
   // User can only specify one -J/-module-dir directory, but may repeat
   // -J/-module-dir as long as the directory is the same each time.
   // https://gcc.gnu.org/onlinedocs/gfortran/Directory-Options.html
diff --git a/flang/test/Driver/write-module.f90 b/flang/test/Driver/write-module.f90
index c4dbaddd4b270..ddced1342f025 100644
--- a/flang/test/Driver/write-module.f90
+++ b/flang/test/Driver/write-module.f90
@@ -3,6 +3,19 @@
 !   * is saved in the _directory specified by the user_
 ! We use `-fsyntax-only` as it stops after the semantic checks (the module file is generated when sema checks are run)
 
+! ------------------------------------------------------------------------------
+! At one time, flang accepted -module-dir<value> (note the lack of a separator
+! between -module-dir and <value>). This is no longer allowed.
+! -module-dir=<value> is also not allowed
+!
+! RUN: not %flang -fsyntax-only -module-dir%t %s 2>&1 \
+! RUN:      | FileCheck %s -check-prefix=JOINED
+!
+! RUN: not %flang -fsyntax-only -module-dir=%t %s 2>&1 \
+! RUN:      | FileCheck %s -check-prefix=JOINED
+!
+! JOINED: error: unknown argument: '-module-dir{{.+}}'
+!
 !--------------------------
 ! -module-dir <value>
 !--------------------------
@@ -10,15 +23,7 @@
 ! RUN: cd %t && %flang -fsyntax-only -module-dir %t/dir-flang %s
 ! RUN: ls %t/dir-flang/testmodule.mod && not ls %t/testmodule.mod
 ! RUN: cd -
-
-!--------------------------
-! -module-dir<value>
-!--------------------------
-! RUN: rm -rf %t && mkdir -p %t/dir-flang
-! RUN: cd %t && %flang -fsyntax-only -module-dir%t/dir-flang %s
-! RUN: ls %t/dir-flang/testmodule.mod && not ls %t/testmodule.mod
-! RUN: cd -
-
+!
 !---------------------------
 ! -J <value>
 !---------------------------

github-actions · 2025-11-19T18:52:56Z

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flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90-pp.f90 flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90.o.ddi

FAILED: flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90-pp.f90 flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90.o.ddi
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/./bin/flang --target=x86_64-unknown-linux-gnu -cpp -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GLIBCXX_NO_ASSERTIONS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/gha/actions-runner/_work/llvm-project/llvm-project/flang-rt/include -I/home/gha/actions-runner/_work/llvm-project/llvm-project/flang-rt/../flang/include -I/home/gha/actions-runner/_work/llvm-project/llvm-project/build/runtimes/runtimes-bins/flang-rt -O3 -module-dirflang-rt/lib/runtime -fno-lto "-D_GLIBCXX_THROW_OR_ABORT(_EXC)=(__builtin_abort())" -E /home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90 > flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90-pp.f90 && /usr/bin/cmake -E cmake_ninja_depends --tdi=flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/FortranDependInfo.json --lang=Fortran --src=flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90-pp.f90 --out=flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90-pp.f90 --dep=flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90-pp.f90.d --obj=flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90.o --ddi=flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/gha/actions-runner/_work/llvm-project/llvm-project/flang/module/iso_fortran_env_impl.f90.o.ddi
flang-22: error: unknown argument: '-module-dirflang-rt/lib/runtime'

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the infrastructure label.

Meinersbur · 2025-11-20T14:00:09Z

As much as I would like this, I fear CMake has to be fixed first: https://gitlab.kitware.com/cmake/cmake/-/blob/master/Modules/Compiler/LLVMFlang-Fortran.cmake?ref_type=heads#L10

tarunprabhu · 2025-11-20T15:03:27Z

As much as I would like this, I fear CMake has to be fixed first: https://gitlab.kitware.com/cmake/cmake/-/blob/master/Modules/Compiler/LLVMFlang-Fortran.cmake?ref_type=heads#L10

I am happy to do that. It's probably better to weed this out if we can because it may well cause us obscure problems in the future.

Replacing the -module-dir in cmake with -J is probably the most reasonable thing to do. -J will work in both joined and separate styles and it is already working as expected in flang, so there should not be any disruption.

Do you have any suggestions on how to go about it? If we do push the change to cmake, do we wait until the next cmake release before merging this in?

tarunprabhu requested review from Meinersbur, banach-space, kiranchandramohan and tblah November 19, 2025 18:23

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

banach-space approved these changes Nov 19, 2025

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[flang][driver] Do not allow -module-dir to be joined to the value #168748

[flang][driver] Do not allow -module-dir to be joined to the value #168748

tarunprabhu commented Nov 19, 2025

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[flang][driver] Do not allow -module-dir to be joined to the value #168748

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