Re: Fwd: [PATCH v2] PE/COFF: Implement visibility attribute via .drectve

LIU Hao <[email protected]> Mon, 10 Aug 2026 18:31:43 +0800
Newsgroups	gmane.comp.gcc.patches
Message-ID	<[email protected]>
在 2026-8-9 22:45, Oleg Tolmatcev 写道:
> ---------- Forwarded message ---------
> От: Oleg Tolmatcev <[email protected]>
> Date: вс, 9 авг. 2026 г. в 16:43
> Subject: [PATCH v2] PE/COFF: Implement visibility attribute via .drectve
> To: <[email protected]>
> Cc: Oleg Tolmatcev <[email protected]>
> 
> 
> On PE/COFF targets (MinGW, Cygwin), the visibility attribute was
> previously ignored with a warning.  This patch makes it functional
> by emitting -exclude-symbols directives into the .drectve section,
> matching Clang's behavior.  The GNU linker already reads and
> respects these directives during auto-export, so hidden/internal
> symbols are now correctly excluded from DLL exports.
> 
> gcc/ChangeLog:
> 
>          * config/mingw/winnt.cc (i386_pe_drectve_name): New.
>          (i386_pe_assemble_visibility): Emit -exclude-symbols
>          directives into .drectve for VISIBILITY_HIDDEN and
>          VISIBILITY_INTERNAL instead of warning.  Use the external
>          symbol spelling for 32-bit PE names.
> 
> gcc/testsuite/ChangeLog:
> 
>          * gcc.target/i386/visibility-hidden-mingw.c: New test.
>          * gcc.target/i386/visibility-hidden-mingw-32.c: New test.
> 
> Signed-off-by: Oleg Tolmatcev <[email protected]>
> ---
>   gcc/config/mingw/winnt.cc                     | 38 +++++++++++++++----
>   .../i386/visibility-hidden-mingw-32.c         | 12 ++++++
>   .../gcc.target/i386/visibility-hidden-mingw.c | 24 ++++++++++++
>   3 files changed, 66 insertions(+), 8 deletions(-)
>   create mode 100644 gcc/testsuite/gcc.target/i386/visibility-hidden-mingw-32.c
>   create mode 100644 gcc/testsuite/gcc.target/i386/visibility-hidden-mingw.c
> 
> diff --git a/gcc/config/mingw/winnt.cc b/gcc/config/mingw/winnt.cc
> index 66d7450652..2e06b0e814 100644
> --- a/gcc/config/mingw/winnt.cc
> +++ b/gcc/config/mingw/winnt.cc
> @@ -254,20 +254,42 @@ i386_pe_maybe_mangle_decl_assembler_name (tree
> decl, tree id)
> 
>   #endif
> 
> +/* Return the symbol spelling used by .drectve exclude-symbols directives.
> +   This is the external name without the user label prefix, while preserving
> +   calling-convention decoration such as fastcall's leading '@' or a
> +   stdcall suffix.  */
> +
> +static const char *
> +i386_pe_drectve_name (tree id)
> +{
> +  const char *name = targetm.strip_name_encoding (IDENTIFIER_POINTER (id));
> +  size_t prefix_len = strlen (user_label_prefix);
> +
> +  if (prefix_len != 0
> +      && strncmp (name, user_label_prefix, prefix_len) == 0)
> +    name += prefix_len;
> +
> +  return name;
> +}
> +
>   /* Emit an assembler directive to set symbol for DECL visibility to
>      the visibility type VIS, which must not be VISIBILITY_DEFAULT.
> -   As for PE there is no hidden support in gas, we just warn for
> -   user-specified visibility attributes.  */
> +   Emit a -exclude-symbols directive into .drectve, compatible with
> +   what Clang emits for hidden visibility on PE/COFF.  */
> 
>   void
> -i386_pe_assemble_visibility (tree decl, int)
> +i386_pe_assemble_visibility (tree decl, int vis)
>   {
> -  if (!decl
> -      || !lookup_attribute ("visibility", DECL_ATTRIBUTES (decl)))
> +  if (!decl)
>       return;
> -  if (!DECL_ARTIFICIAL (decl))
> -    warning (OPT_Wattributes, "visibility attribute not supported "
> -                             "in this configuration; ignored");
> +
> +  if (vis == VISIBILITY_HIDDEN || vis == VISIBILITY_INTERNAL)
> +    {
> +      tree id = DECL_ASSEMBLER_NAME (decl);
> +      const char *name = i386_pe_drectve_name (id);
> +      drectve_section ();
> +      fprintf (asm_out_file, "\t.ascii \" -exclude-symbols:%s\"\n", name);
> +    }
>   }
> 
>   #if !defined (TARGET_AARCH64_MS_ABI)
> diff --git a/gcc/testsuite/gcc.target/i386/visibility-hidden-mingw-32.c
> b/gcc/testsuite/gcc.target/i386/visibility-hidden-mingw-32.c
> new file mode 100644
> index 0000000000..a952c71a01
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/visibility-hidden-mingw-32.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile { target i?86-*-mingw32* i?86-*-cygwin* } } */
> +/* { dg-options "-fvisibility=hidden" } */
> +
> +void some_cdecl (int, int) {}
> +void __attribute__((stdcall)) some_stdcall (int, int) {}
> +void __attribute__((fastcall)) some_fastcall (int, int) {}
> +
> +/* Hidden visibility on 32-bit PE/COFF drops the user label prefix in
> +   .drectve, but keeps stdcall and fastcall decoration.  */
> +/* { dg-final { scan-assembler {-exclude-symbols:some_cdecl} } } */
> +/* { dg-final { scan-assembler {-exclude-symbols:some_stdcall@8} } } */
> +/* { dg-final { scan-assembler {-exclude-symbols:@some_fastcall@8} } } */
> diff --git a/gcc/testsuite/gcc.target/i386/visibility-hidden-mingw.c
> b/gcc/testsuite/gcc.target/i386/visibility-hidden-mingw.c
> new file mode 100644
> index 0000000000..12d792631d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/visibility-hidden-mingw.c
> @@ -0,0 +1,24 @@
> +/* { dg-do link { target *-*-mingw* *-*-cygwin* } } */
> +/* { dg-require-dll "" } */
> +/* { dg-options "-shared -fvisibility=hidden
> -Wl,--output-def,visibility-hidden-mingw.def" } */
> +
> +void __attribute__((visibility("default"))) exported_func(void) {}
> +void hidden_func(void) {}
> +void __attribute__((visibility("hidden"))) explicit_hidden_func(void) {}
> +void __attribute__((visibility("internal"))) internal_func(void) {}
> +
> +/* exported_func has default visibility, so it should be exported.  */
> +/* { dg-final { scan-file visibility-hidden-mingw.def
> "(?n)^\\s*exported_func(?:\\s+@\[0-9\]+)?$" } } */
> +
> +/* hidden_func gets hidden from -fvisibility=hidden, so it should not be
> +   auto-exported.  */
> +/* { dg-final { scan-file-not visibility-hidden-mingw.def
> "(?n)^\\s*hidden_func(?:\\s+@\[0-9\]+)?$" } } */
> +
> +/* explicit_hidden_func is explicitly hidden, so it should not be
> +   auto-exported.  */
> +/* { dg-final { scan-file-not visibility-hidden-mingw.def
> "(?n)^\\s*explicit_hidden_func(?:\\s+@\[0-9\]+)?$" } } */
> +
> +/* internal_func has internal visibility, so it should not be
> auto-exported.  */
> +/* { dg-final { scan-file-not visibility-hidden-mingw.def
> "(?n)^\\s*internal_func(?:\\s+@\[0-9\]+)?$" } } */
> +
> +/* { dg-final { remove-build-file "visibility-hidden-mingw.def" } } */
> --
> 2.55.0.windows.3

I have tested this change on {x86_64,i686}-w64-mingw32 and both look good to me. Thanks.





-- 
Best regards,
LIU Hao
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