The same error is given by Clang/LLVM.
Tested on x86_64-w64-mingw32, OK for the mainline?
2026-01-26 Eric Botcazou <[email protected]>
PR target/80881
* attribs.cc (handle_dll_attribute): If TARGET_WIN32_TLS is 1,
issue an error if either attribute is set on a TLS variable.
2026-01-26 Eric Botcazou <[email protected]>
* c-c++-common/tls-attr-dll.c: New test.
--
Eric Botcazoudiff --git a/gcc/attribs.cc b/gcc/attribs.cc
index db9a5c125ac..d802136655c 100644
--- a/gcc/attribs.cc
+++ b/gcc/attribs.cc
@@ -2007,10 +2007,16 @@ handle_dll_attribute (tree * pnode, tree name, tree args, int flags,
{
if (DECL_INITIAL (node))
{
- error ("variable %q+D definition is marked dllimport",
- node);
+ error ("variable %q+D definition is marked dllimport", node);
*no_add_attrs = true;
}
+#if TARGET_WIN32_TLS
+ else if (DECL_THREAD_LOCAL_P (node))
+ {
+ error ("thread-local variable %q+D declared as dllimport", node);
+ *no_add_attrs = true;
+ }
+#endif
/* `extern' needn't be specified with dllimport.
Specify `extern' now and hope for the best. Sigh. */
@@ -2034,6 +2040,13 @@ handle_dll_attribute (tree * pnode, tree name, tree args, int flags,
&& flag_keep_inline_dllexport)
/* An exported function, even if inline, must be emitted. */
DECL_EXTERNAL (node) = 0;
+#if TARGET_WIN32_TLS
+ else if (VAR_P (node) && DECL_THREAD_LOCAL_P (node))
+ {
+ error ("thread-local variable %q+D declared as dllexport", node);
+ *no_add_attrs = true;
+ }
+#endif
/* Report error if symbol is not accessible at global scope. */
if (!TREE_PUBLIC (node) && VAR_OR_FUNCTION_DECL_P (node))
/* { dg-do compile { target i?86-*-mingw* x86_64-*-mingw* } } */
__declspec (dllimport) __thread int foo1; /* { dg-error "thread-local variable" } */
__declspec (dllexport) __thread int foo2; /* { dg-error "thread-local variable" } */
