[gcc r17-3292] gcc/mingw32: Do not export `HOST_EXTRA_OBJS_SYMBOL`

https://gcc.gnu.org/g:c7282ce59753dd809ca567d045dc356d56b88fe2

commit r17-3292-gc7282ce59753dd809ca567d045dc356d56b88fe2
Author: LIU Hao <[email protected]>
Date:   Mon Aug 10 13:56:09 2026 +0800

    gcc/mingw32: Do not export `HOST_EXTRA_OBJS_SYMBOL`
    
    When building with `--enable-plugin`, the linker is passed `--export-all-symbols`
    so it attempts to export `HOST_EXTRA_OBJS_SYMBOL` which is an artificial symbol
    and is not prefixed with an underscore. For i686, the convention is that if the
    linker is told to export `foo`, it looks for `_foo`. Therefore in this case it
    attempts to export `_HOST_EXTRA_OBJS_SYMBOL` which isn't defined:
    
       ld.exe: cannot export HOST_EXTRA_OBJS_SYMBOL: symbol not found
       collect2.exe: error: ld returned 1 exit status
    
    Since this symbol is only used to create a reference to pull in the manifest
    resource for an image, the fix is to mark it as `visibility("hidden")` so it
    will not be exported, despite `--export-all-symbols`.
    
    In addition, since this is a C++ file, `extern "C"` is added for correctness.
    
    gcc/ChangeLog:
    
            * config/i386/sym-mingw32.cc: Add `extern "C"` and `visibility("hidden")`.
    
    Signed-off-by: Jonathan Yong <[email protected]>

Diff:
---
 gcc/config/i386/sym-mingw32.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/gcc/config/i386/sym-mingw32.cc b/gcc/config/i386/sym-mingw32.cc
index 2f8dee6c1ecd..5403dd2cfe98 100644
--- a/gcc/config/i386/sym-mingw32.cc
+++ b/gcc/config/i386/sym-mingw32.cc
@@ -1,3 +1,4 @@
 /* Prevent any name mangling to make sure that the linker
    will always find the symbol. */
+extern "C" __attribute__ ((visibility ("hidden")))
 char HOST_EXTRA_OBJS_SYMBOL asm ("HOST_EXTRA_OBJS_SYMBOL");