[flang] Downgrade error to warning for consistency #157191
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When a procedure name is declared EXTERNAL and then followed up with an explicit INTERFACE, the compiler emits an error when the procedure is a dummy procedure but only a warning otherwise. Since the EXTERNAL statement is harmless in both cases, accept the case of a dummy procedure as well for consistency. Fixes llvm#157162.
llvmbot
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flang
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@llvm/pr-subscribers-flang-semantics Author: Peter Klausler (klausler) ChangesWhen a procedure name is declared EXTERNAL and then followed up with an explicit INTERFACE, the compiler emits an error when the procedure is a dummy procedure but only a warning otherwise. Since the EXTERNAL statement is harmless in both cases, accept the case of a dummy procedure as well for consistency. Fixes #157162. Full diff: https://github.com/llvm/llvm-project/pull/157191.diff 3 Files Affected:
diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index 4720932780472..077bee930675e 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -646,12 +646,18 @@ class ScopeHandler : public ImplicitRulesVisitor {
}
if (symbol->CanReplaceDetails(details)) {
// update the existing symbol
- CheckDuplicatedAttrs(name, *symbol, attrs);
- SetExplicitAttrs(*symbol, attrs);
if constexpr (std::is_same_v<SubprogramDetails, D>) {
// Dummy argument defined by explicit interface?
details.set_isDummy(IsDummy(*symbol));
+ if (symbol->has<ProcEntityDetails>()) {
+ // Bare "EXTERNAL" dummy replaced with explicit INTERFACE
+ context().Warn(common::LanguageFeature::RedundantAttribute, name,
+ "Dummy argument '%s' was declared earlier as EXTERNAL"_warn_en_US,
+ name);
+ }
}
+ CheckDuplicatedAttrs(name, *symbol, attrs);
+ SetExplicitAttrs(*symbol, attrs);
symbol->set_details(std::move(details));
return *symbol;
} else if constexpr (std::is_same_v<UnknownDetails, D>) {
diff --git a/flang/lib/Semantics/symbol.cpp b/flang/lib/Semantics/symbol.cpp
index a6b402c48d4ff..ea7eeac80a2d9 100644
--- a/flang/lib/Semantics/symbol.cpp
+++ b/flang/lib/Semantics/symbol.cpp
@@ -330,8 +330,14 @@ bool Symbol::CanReplaceDetails(const Details &details) const {
common::visitors{
[](const UseErrorDetails &) { return true; },
[&](const ObjectEntityDetails &) { return has<EntityDetails>(); },
- [&](const ProcEntityDetails &) { return has<EntityDetails>(); },
+ [&](const ProcEntityDetails &x) { return has<EntityDetails>(); },
[&](const SubprogramDetails &) {
+ if (const auto *oldProc{detailsIf<ProcEntityDetails>()}) {
+ // Can replace bare "EXTERNAL dummy" with explicit INTERFACE
+ return oldProc->isDummy() && !oldProc->procInterface() &&
+ attrs().test(Attr::EXTERNAL) && !test(Flag::Function) &&
+ !test(Flag::Subroutine);
+ }
return has<SubprogramNameDetails>() || has<EntityDetails>();
},
[&](const DerivedTypeDetails &) {
@@ -339,14 +345,12 @@ bool Symbol::CanReplaceDetails(const Details &details) const {
return derived && derived->isForwardReferenced();
},
[&](const UseDetails &x) {
- const auto *use{this->detailsIf<UseDetails>()};
+ const auto *use{detailsIf<UseDetails>()};
return use && use->symbol() == x.symbol();
},
- [&](const HostAssocDetails &) {
- return this->has<HostAssocDetails>();
- },
+ [&](const HostAssocDetails &) { return has<HostAssocDetails>(); },
[&](const UserReductionDetails &) {
- return this->has<UserReductionDetails>();
+ return has<UserReductionDetails>();
},
[](const auto &) { return false; },
},
diff --git a/flang/test/Semantics/resolve20.f90 b/flang/test/Semantics/resolve20.f90
index 8b8d190206689..f1a1a30cc714e 100644
--- a/flang/test/Semantics/resolve20.f90
+++ b/flang/test/Semantics/resolve20.f90
@@ -89,4 +89,12 @@ subroutine test
!ERROR: Abstract procedure interface 'f' may not be referenced
x = f()
end subroutine
+ subroutine baz(foo)
+ external foo
+ interface
+ !WARNING: Dummy argument 'foo' was declared earlier as EXTERNAL [-Wredundant-attribute]
+ subroutine foo(x)
+ end
+ end interface
+ end
end module
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eugeneepshteyn
approved these changes
Sep 7, 2025
kkwli
approved these changes
Sep 8, 2025
|
Sorry, I miss this case. Should it be covered in this fix? interface
subroutine g(f)
external f
interface
subroutine f()
end
end interface
end
end interface
endOutput: |
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If interface
subroutine g()
external f
interface
subroutine f()
end
end interface
end
end interface
endOutput: |
@klausler My bad! I messed up the build! A warning message is emitted in both cases. Everything looks fine. |
Thanks for checking. |
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What happened to the CI checks in this PR? |
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When a procedure name is declared EXTERNAL and then followed up with an explicit INTERFACE, the compiler emits an error when the procedure is a dummy procedure but only a warning otherwise. Since the EXTERNAL statement is harmless in both cases, accept the case of a dummy procedure as well for consistency.
Fixes #157162.