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c++/modules: Give more specific diagnostics in is_matching_decl

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This patch also rephrases the diagnostics to talk about "imported
declarations" rather than "global module declarations", since as the
FIXME noted we can also get mismatches with some declarations attached
to modules.  Ideally I'd like to revisit the way this is structured
entirely but that won't be appropriate for GCC 15.

gcc/cp/ChangeLog:

	* module.cc (trees_in::is_matching_decl): Add custom errors for
	different kinds of mismatches.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/lambda-8_b.C: Adjust error.
	* g++.dg/modules/leg-merge-4_c.C: Likewise.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
This commit is contained in:
Nathaniel Shead 2025-04-11 07:09:33 +10:00
parent 171710bec5
commit 714e9020be
3 changed files with 47 additions and 16 deletions
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55
gcc/cp/module.cc
View file

@ -12090,6 +12090,8 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
gcc_checking_assert (TREE_CODE (e_inner) == TREE_CODE (d_inner));
}
// FIXME: do more precise errors at point of mismatch
const char *mismatch_msg = nullptr;
if (TREE_CODE (d_inner) == FUNCTION_DECL)
{
tree e_ret = fndecl_declared_return_type (existing);
@ -12099,13 +12101,20 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
&& LAMBDA_TYPE_P (DECL_CONTEXT (d_inner)))
/* This has a recursive type that will compare different. */;
else if (!same_type_p (d_ret, e_ret))
goto mismatch;
{
mismatch_msg = G_("conflicting type for imported declaration %#qD");
goto mismatch;
}
tree e_type = TREE_TYPE (e_inner);
tree d_type = TREE_TYPE (d_inner);
if (DECL_EXTERN_C_P (d_inner) != DECL_EXTERN_C_P (e_inner))
goto mismatch;
{
mismatch_msg = G_("conflicting language linkage for imported "
"declaration %#qD");
goto mismatch;
}
for (tree e_args = TYPE_ARG_TYPES (e_type),
d_args = TYPE_ARG_TYPES (d_type);
@ -12113,10 +12122,18 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
e_args = TREE_CHAIN (e_args), d_args = TREE_CHAIN (d_args))
{
if (!(e_args && d_args))
goto mismatch;
{
mismatch_msg = G_("conflicting argument list for imported "
"declaration %#qD");
goto mismatch;
}
if (!same_type_p (TREE_VALUE (d_args), TREE_VALUE (e_args)))
goto mismatch;
{
mismatch_msg = G_("conflicting argument types for imported "
"declaration %#qD");
goto mismatch;
}
}
/* If EXISTING has an undeduced or uninstantiated exception
@ -12149,7 +12166,11 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
}
else if (!DEFERRED_NOEXCEPT_SPEC_P (d_spec)
&& !comp_except_specs (d_spec, e_spec, ce_type))
goto mismatch;
{
mismatch_msg = G_("conflicting %<noexcept%> specifier for "
"imported declaration %#qD");
goto mismatch;
}
/* Similarly if EXISTING has an undeduced return type, but DECL's
is already deduced. */
@ -12163,7 +12184,11 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
}
else if (type_uses_auto (d_ret)
&& !same_type_p (TREE_TYPE (d_type), TREE_TYPE (e_type)))
goto mismatch;
{
mismatch_msg = G_("conflicting deduced return type for "
"imported declaration %#qD");
goto mismatch;
}
/* Similarly if EXISTING has undeduced constexpr, but DECL's
is already deduced. */
@ -12172,7 +12197,11 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
DECL_DECLARED_CONSTEXPR_P (e_inner) = true;
else if (DECL_DECLARED_CONSTEXPR_P (e_inner)
!= DECL_DECLARED_CONSTEXPR_P (d_inner))
goto mismatch;
{
mismatch_msg = G_("conflicting %<constexpr%> for imported "
"declaration %#qD");
goto mismatch;
}
/* Don't synthesize a defaulted function if we're importing one
we've already determined. */
@ -12184,13 +12213,17 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
if (!DECL_ORIGINAL_TYPE (e_inner)
|| !same_type_p (DECL_ORIGINAL_TYPE (d_inner),
DECL_ORIGINAL_TYPE (e_inner)))
goto mismatch;
{
mismatch_msg = G_("conflicting imported declaration %q#D");
goto mismatch;
}
}
/* Using cp_tree_equal because we can meet TYPE_ARGUMENT_PACKs
here. I suspect the entities that directly do that are things
that shouldn't go to duplicate_decls (FIELD_DECLs etc). */
else if (!cp_tree_equal (TREE_TYPE (decl), TREE_TYPE (existing)))
{
mismatch_msg = G_("conflicting type for imported declaration %#qD");
mismatch:
if (DECL_IS_UNDECLARED_BUILTIN (existing))
/* Just like duplicate_decls, presum the user knows what
@ -12203,11 +12236,9 @@ trees_in::is_matching_decl (tree existing, tree decl, bool is_typedef)
equality isn't feasible in general for local entities. */;
else
{
// FIXME:QOI Might be template specialization from a module,
// not necessarily global module
gcc_checking_assert (mismatch_msg);
auto_diagnostic_group d;
error_at (DECL_SOURCE_LOCATION (decl),
"conflicting global module declaration %#qD", decl);
error_at (DECL_SOURCE_LOCATION (decl), mismatch_msg, decl);
inform (DECL_SOURCE_LOCATION (existing),
"existing declaration %#qD", existing);
return false;

2
gcc/testsuite/g++.dg/modules/lambda-8_b.C
View file

@ -4,4 +4,4 @@
#include "lambda-8.h"
import "lambda-8_a.H";
// { dg-error "conflicting global module declaration" "" { target *-*-* } 0 }
// { dg-error "conflicting imported declaration" "" { target *-*-* } 0 }

6
gcc/testsuite/g++.dg/modules/leg-merge-4_c.C
View file

@ -11,8 +11,8 @@ void foo ()
X *p;
}
// { dg-regexp "\nIn module \[^\n]*leg-merge-4_b.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_b.H:4:\[0-9]*: error: conflicting global module declaration 'float bob'\nIn module \[^\n]*leg-merge-4_a.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_a.H:4:\[0-9]*: note: existing declaration 'int bob'\n\[^\n]*leg-merge-4_c.C:9:\[0-9]*: note: during load of binding '::bob'$" }
// { dg-regexp "\nIn module \[^\n]*leg-merge-4_b.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_b.H:4:\[0-9]*: error: conflicting type for imported declaration 'float bob'\nIn module \[^\n]*leg-merge-4_a.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_a.H:4:\[0-9]*: note: existing declaration 'int bob'\n\[^\n]*leg-merge-4_c.C:9:\[0-9]*: note: during load of binding '::bob'$" }
// { dg-regexp "\nIn module \[^\n]*leg-merge-4_b.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_b.H:5:\[0-9]*: error: conflicting global module declaration 'int frob\\(\\)'\nIn module \[^\n]*leg-merge-4_a.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_a.H:5:\[0-9]*: note: existing declaration 'void frob\\(\\)'\n\[^\n]*leg-merge-4_c.C:10:\[0-9]*: note: during load of binding '::frob'$" }
// { dg-regexp "\nIn module \[^\n]*leg-merge-4_b.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_b.H:5:\[0-9]*: error: conflicting type for imported declaration 'int frob\\(\\)'\nIn module \[^\n]*leg-merge-4_a.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_a.H:5:\[0-9]*: note: existing declaration 'void frob\\(\\)'\n\[^\n]*leg-merge-4_c.C:10:\[0-9]*: note: during load of binding '::frob'$" }
// { dg-regexp "In module \[^\n]*leg-merge-4_b.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_b.H:6:\[0-9]*: error: conflicting global module declaration 'union X'\nIn module \[^\n]*leg-merge-4_a.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_a.H:6:\[0-9]*: note: existing declaration 'class X'\n\[^\n]*leg-merge-4_c.C:11:\[0-9]*: note: during load of binding '::X'$" }
// { dg-regexp "In module \[^\n]*leg-merge-4_b.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_b.H:6:\[0-9]*: error: conflicting type for imported declaration 'union X'\nIn module \[^\n]*leg-merge-4_a.H, imported at \[^\n]*leg-merge-4_c.C:\[0-9]*:\n\[^\n]*leg-merge-4_a.H:6:\[0-9]*: note: existing declaration 'class X'\n\[^\n]*leg-merge-4_c.C:11:\[0-9]*: note: during load of binding '::X'$" }