Exporting symbols with 8445 characters or more gets them subdivided into multiple symbols on Windows

[Fulgen301]

I tried this code (reproducer attached: test.rs.txt):

#[unsafe(no_mangle)]
fn AAAA....8445 As in total....A() {}

I expected to see this happen: It works.

Instead, this happened: It gets turned into two symbols:

error: linking with `link.exe` failed: exit code: 1120
  |
  = note: "C:\\Program Files\\Microsoft Visual Studio\\18\\Insiders\\VC\\Tools\\MSVC\\14.50.35503\\bin\\HostX64\\x64\\link.exe" "/DEF:C:\\Users\\tokgeo\\AppData\\Local\\Temp\\rustc6LxeaL\\lib.def" "/NOLOGO" "C:\\Users\\tokgeo\\AppData\\Local\\Temp\\rustc6LxeaL\\symbols.o" "<2 object files omitted>" "<sysroot>\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib/{libstd-*,libpanic_unwind-*,libwindows_targets-*,librustc_demangle-*,libstd_detect-*,libhashbrown-*,librustc_std_workspace_alloc-*,libunwind-*,libcfg_if-*,librustc_std_workspace_core-*,liballoc-*,libcore-*,libcompiler_builtins-*}.rlib" "kernel32.lib" "kernel32.lib" "kernel32.lib" "ntdll.lib" "userenv.lib" "ws2_32.lib" "dbghelp.lib" "/defaultlib:msvcrt" "/NXCOMPAT" "/OUT:test.dll" "/OPT:REF,NOICF" "/DLL" "/IMPLIB:test.dll.lib" "/DEBUG" "/PDBALTPATH:%_PDB%" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\intrinsic.natvis" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\liballoc.natvis" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\libcore.natvis" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\libstd.natvis"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: lib.def : error LNK2001: Nicht aufgelöstes externes Symbol "A".␍
          lib.def : error LNK2001: Nicht aufgelöstes externes Symbol "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

followed by the rest of the As.

Keeping the symbol name at <= 8444 characters links with no issues.

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rustc --version --verbose:

rustc 1.92.0-nightly (1d23d0680 2025-10-22)
binary: rustc
commit-hash: 1d23d06800271f651fad07bf22bf5e298138972e
commit-date: 2025-10-22
host: x86_64-pc-windows-msvc
release: 1.92.0-nightly
LLVM version: 21.1.3

[Fulgen301]

This is a bug within link.exe - the .def file generated by rustc is correct, the linker divides it into multiple symbols.

Reported.