https://gcc.gnu.org/g:baa4e4ddf800602d818470ef493d3508c4e1e32a
commit r17-3189-gbaa4e4ddf800602d818470ef493d3508c4e1e32a Author: Oleg Tolmatcev <[email protected]> Date: Sun Aug 9 16:41:31 2026 +0200 PE/COFF: Implement visibility attribute via .drectve 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]> Signed-off-by: Jonathan Yong <[email protected]> Diff: --- gcc/config/mingw/winnt.cc | 38 +++++++++++++++++----- .../gcc.target/i386/visibility-hidden-mingw-32.c | 12 +++++++ .../gcc.target/i386/visibility-hidden-mingw.c | 24 ++++++++++++++ 3 files changed, 66 insertions(+), 8 deletions(-) diff --git a/gcc/config/mingw/winnt.cc b/gcc/config/mingw/winnt.cc index 66d7450652d2..2e06b0e81462 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 000000000000..a952c71a013f --- /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 000000000000..12d792631d4b --- /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" } } */
