[clang] Fix libclang linking on Solaris

[ro]

Summary

Linking libclang.so is currently broken on Solaris:

ld: fatal: option --version-script requires option -z gnu-version-script-compat to be specified

While Solaris ld supports a considerable subset of --version-script, there are some
elements of the syntax that aren't.

The fix is equivalent to D78510. Additionally, use C-style comments is a GNU extension
that can easily be avoided by using # as comment character.

Tested on amd64-pc-solaris2.11 and sparcv9-sun-solaris2.11.

[MaskRay]

clang/tools/libclang/libclang.map

1–5

GNU ld doesn't support # comments. ld.lld supports it.

[tstellar]

Is there any kind of comment that is supported by all linkers?

[MaskRay]

ld.lld, GNU ld, and gold support /* */. I am not sure about Solaris ld -z gnu-version-script-compat.

[ro]

In D107559#2928851, @tstellar wrote:

Is there any kind of comment that is supported by all linkers?

Seems there isn't. In that case, we could either move the comments to a separate file (libclang.README?), strip the comments when using
Solaris ld (a bit ugly), or have two separate version scripts (terrible, bound to diverge).

In D107559#2928972, @MaskRay wrote:

ld.lld, GNU ld, and gold support /* */. I am not sure about Solaris ld -z gnu-version-script-compat.

Not sure in which way? Support for /* */ comments (no) or need for the option? The latter is explained in ld(1):

-z gnu-version-script=mapfile
-z gnu-version-script-compat
--version-script mapfile

    Provides partial support for the GNU version script style  of  map-
    file.  Version  scripts are based on the original Solaris version 1
    symbol definition syntax, with some  extensions.  ld  supports  the
    most  common  such extension, the use of wildcard characters in the
    specified symbol names. Other GNU-specific extensions  may  not  be
    supported.  ld  will  issue  an appropriate error if an unsupported
    extension is encountered.

    For convenience in building software  developed  with  GNU  version
    scripts,  the native GNU  --version-script option is accepted as an
    alias for -z gnu-version-script. Due to the partial nature  of  the
    support  for  GNU version scripts, the use of --version-script must
    be explicitly enabled by specifying -z gnu-version-script-compat.

clang/tools/libclang/libclang.map

1–5

Drats, I'd have sworn they supported `#' comments, too,
especially since the version script syntax originated with
Sun and was later adopted by GNU ld.

[tstellar]

In D107559#2928999, @ro wrote:

In D107559#2928851, @tstellar wrote:

Is there any kind of comment that is supported by all linkers?

Seems there isn't. In that case, we could either move the comments to a separate file (libclang.README?), strip the comments when using
Solaris ld (a bit ugly), or have two separate version scripts (terrible, bound to diverge).

I think it would be better to move the comments to libclang.README.

[MaskRay]

clang/tools/libclang/libclang.map

1–5

Confirmed that GNU ld and gold support # in version scripts, but not in linker scripts.

ld.lld supports both.

Using # is fine to me if Solaris ld doesn't support /* in GNU version scripts.

[MaskRay]

clang/tools/libclang/libclang.map

1–5

Correction: only GNU ld doesn't support # in linker scripts.

ld.lld and gold support # everywhere.

Filed a GNU ld feature request https://sourceware.org/bugzilla/show_bug.cgi?id=28198

[ro]

clang/tools/libclang/libclang.map

1–5

I'd only checked ld.texi and didn't even think of trying it when it wasn't documented there.

I can ask about C-style comments being added to Solaris ld, but I've never encountered the need before.

So the original patch is ok after all?

[ro]

Ah, I forgot: I've meanwhile tested the patch on x86-64-pc-linux-gnu (Ubuntu 20.04) where /usr/bin/ld is from binutils 2.34: libclang.so was versioned just the same without and with the patch.

[MaskRay]

# LG

clang/tools/libclang/CMakeLists.txt

else()
     if(LLVM_ENABLE_MODULES AND NOT WIN32)
       target_compile_options(libclang PRIVATE
         "-fmodules-ignore-macro=_CINDEX_LIB_"
         )
     endif()
   endif()
   if (USE_VERSION_SCRIPT)
     target_link_options(libclang PRIVATE "-Wl,--version-script,${CMAKE_CURRENT_SOURCE_DIR}/libclang.map")
+    # The Solaris 11.4 linker supports a subset of GNU ld version scripts,
+    # but requires a special option to enable it.
+    if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+      target_link_options(libclang PRIVATE "-Wl,-z,gnu-version-script-compat")
+    endif()
     # Ensure that libclang.so gets rebuilt when the linker script changes.
     set_property(SOURCE ARCMigrate.cpp APPEND PROPERTY
                  OBJECT_DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/libclang.map)
 
     # The SOVERSION should be updated only if a change is made to the libclang
     # ABI, and when it is updated, it should be updated to the current
     # LLVM_VERSION_MAJOR.
     set_target_properties(libclang PROPERTIES

clang/tools/libclang/libclang.map

-/* If you add a symbol to this file, make sure to add it with the correct
- * version.  For example, if the LLVM main branch is LLVM 14.0.0, add new
- * symbols with the version LLVM_14.
- * On platforms where versions scripts are not used, this file will be used to
- * generate a list of exports for libclang.so
- */
-
+# If you add a symbol to this file, make sure to add it with the correct
+# version.  For example, if the LLVM main branch is LLVM 14.0.0, add new
+# symbols with the version LLVM_14.
+# On platforms where versions scripts are not used, this file will be used to
+# generate a list of exports for libclang.so
 
 LLVM_13 {
   global:
     clang_BlockCommandComment_getArgText;
     clang_BlockCommandComment_getCommandName;
     clang_BlockCommandComment_getNumArgs;
     clang_BlockCommandComment_getParagraph;
     clang_CXCursorSet_contains;
global:
     clang_tokenize;
     clang_uninstall_llvm_fatal_error_handler;
     clang_visitChildren;
     clang_visitChildrenWithBlock;
 
   local: *;
 };
 
-/* Example of how to add a new symbol version entry.  If you do add a new symbol
- * version, please update the example to depend on the version you added.
- * LLVM_X {
- * global:
- *    clang_newsymbol;
- * };
- */
+# Example of how to add a new symbol version entry.  If you do add a new symbol
+# version, please update the example to depend on the version you added.
+# LLVM_X {
+# global:
+#   clang_newsymbol;
+# };