[libcxx] [test] Use -fms-runtime-lib= for picking the CRT to use

[mstorsjo]

Summary

This is a more correct way of linking against a specific runtime
library with the GCC-like clang frontend.

This avoids having to pass -D_DEBUG (and passes flags like -D_DLL,
which we should be passing if linking against the dynamic CRT).

When -fms-runtime-lib= is specified, each compiled object file gets
embedded directives instructing the linker about what CRT it should
link against. The -nostdlib we pass to the compiler driver only
inhibits the libs that the compiler driver passes to the linker
command.

Thus, this also avoids having to specify -lmsvcrt, -lmsvcrtd,
-llibcmt or -llibcmtd and -loldnames.

Based on a patch by Andrew Ng.

The -fms-runtime-lib= option was added in Clang 16, so this patch
can only be landed once libcxx's compiler requirement has been
bumped to Clang 16 (which is expected to be done sometime after
Clang 17 has been branched or released).

[andrewng]

This LGTM but perhaps this should be rolled in with or done after the de-duplication of these test config files?

[mstorsjo]

In D155562#4534455, @andrewng wrote:

This LGTM but perhaps this should be rolled in with or done after the de-duplication of these test config files?

Dunno - I'm keeping it separate at least, to allow a separate decision on whether such a deduplication (moving more config-specific logic from the test configs into cmake) is a good or bad thing.

[mstorsjo]

Rebased

[mstorsjo]

After rebasing, there were some unrelated test failures in the module build here.

[mstorsjo]

Rebased, with the deduplication done before this.

[mstorsjo]

Rebase

[mstorsjo]

Rebase

[Mordante]

LGTM but please wait for clang-16 to be the minimal supported Clang version and wait for the approval of @andrewng

[ldionne]

[Github PR transition cleanup]

This patch makes sense to me. I am dropping Clang 15 here: https://github.com/llvm/llvm-project/pull/66406.

Can you please rebase to poke CI and ship this once the above PR has been merged? I'll make a note to ping here when I merge it.

[ldionne]

@mstorsjo Can you rebase this now? I just dropped support for Clang 15.

[mstorsjo]

Rebased, rerunning CI, will land if things look fine.

[mstorsjo]

In D155562#4651017, @mstorsjo wrote:

Rebased, rerunning CI, will land if things look fine.

The CI mostly completed; the benchmarks build seems to have failed due to something unrelated, and a few macOS jobs are still waiting 14h later; I'll go ahead and land this.

libcxx/test/CMakeLists.txt

 endif()
 
 if (MSVC)
   # Shared code for initializing some parameters used by all
   # llvm-libc++-*-clangcl.cfg.in test configs.
   set(dbg_include "")
 
   if (NOT CMAKE_MSVC_RUNTIME_LIBRARY OR CMAKE_MSVC_RUNTIME_LIBRARY MATCHES "DLL$")
-    set(crt_lib "msvcrt")
+    set(fms_runtime_lib "dll")
     set(cxx_lib "msvcprt")
   else()
-    set(crt_lib "libcmt")
+    set(fms_runtime_lib "static")
     set(cxx_lib "libcpmt")
   endif()
 
   if ((NOT CMAKE_MSVC_RUNTIME_LIBRARY AND uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
       OR (CMAKE_MSVC_RUNTIME_LIBRARY MATCHES "Debug"))
-    set(dbg_include " -D_DEBUG -include set_windows_crt_report_mode.h")
-    set(crt_lib "${crt_lib}d")
+    set(dbg_include " -include set_windows_crt_report_mode.h")
+    set(fms_runtime_lib "${fms_runtime_lib}_dbg")
     set(cxx_lib "${cxx_lib}d")
   endif()
 
   serialize_lit_param(dbg_include "\"${dbg_include}\"")
-  serialize_lit_param(crt_lib "\"${crt_lib}\"")
+  serialize_lit_param(fms_runtime_lib "\"${fms_runtime_lib}\"")
   serialize_lit_param(cxx_lib "\"${cxx_lib}\"")
 endif()
 
 if (LIBCXX_INCLUDE_TESTS)
   include(AddLLVM) # for configure_lit_site_cfg and add_lit_testsuite
 
   configure_file("${CMAKE_CURRENT_SOURCE_DIR}/configs/cmake-bridge.cfg.in"
                  "${CMAKE_CURRENT_BINARY_DIR}/cmake-bridge.cfg"

libcxx/test/configs/llvm-libc++-shared-clangcl.cfg.in

 # This testing configuration handles running the test suite against LLVM's libc++
 # using a DLL, with Clang-cl on Windows.
 
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}', '--driver-mode=g++'))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX' + config.dbg_include
+    '-fms-runtime-lib=' + config.fms_runtime_lib + ' -nostdinc++ -I %{include} -I %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX' + config.dbg_include
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib -L %%{lib} -lc++ -l%s -l%s -loldnames' % (config.crt_lib, config.cxx_lib)
+    '-nostdlib -L %{lib} -lc++ -l' + config.cxx_lib
 ))
 config.substitutions.append(('%{exec}',
     '%{executor} --execdir %T --prepend_env PATH=%{lib} -- '
 ))
 
 import os, site
 site.addsitedir(os.path.join('@LIBCXX_SOURCE_DIR@', 'utils'))
 import libcxx.test.params, libcxx.test.config
 libcxx.test.config.configure(
     libcxx.test.params.DEFAULT_PARAMETERS,
     libcxx.test.features.DEFAULT_FEATURES,
     config,
     lit_config
 )

libcxx/test/configs/llvm-libc++-shared-no-vcruntime-clangcl.cfg.in

 # This testing configuration handles running the test suite against LLVM's libc++
 # using a DLL, with Clang-cl on Windows. This variant sets _HAS_EXCEPTIONS = 0
 # which removes exception class definitions from the vcruntime.
 
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}', '--driver-mode=g++'))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX -D_HAS_EXCEPTIONS=0' + config.dbg_include
+    '-fms-runtime-lib=' + config.fms_runtime_lib + ' -nostdinc++ -I %{include} -I %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX -D_HAS_EXCEPTIONS=0' + config.dbg_include
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib -L %%{lib} -lc++ -l%s -l%s -loldnames' % (config.crt_lib, config.cxx_lib)
+    '-nostdlib -L %{lib} -lc++ -l' + config.cxx_lib
 ))
 config.substitutions.append(('%{exec}',
     '%{executor} --execdir %T --prepend_env PATH=%{lib} -- '
 ))
 
 import os, site
 site.addsitedir(os.path.join('@LIBCXX_SOURCE_DIR@', 'utils'))
 import libcxx.test.params, libcxx.test.config
 libcxx.test.config.configure(
     libcxx.test.params.DEFAULT_PARAMETERS,
     libcxx.test.features.DEFAULT_FEATURES,
     config,
     lit_config
 )

libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in

 # This testing configuration handles running the test suite against LLVM's libc++
 # using a static library, with Clang-cl on Windows.
 
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}', '--driver-mode=g++'))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -I %{include} -I %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX' + config.dbg_include
+    '-fms-runtime-lib=' + config.fms_runtime_lib + ' -nostdinc++ -I %{include} -I %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX' + config.dbg_include
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib -L %%{lib} -llibc++ -l%s -l%s -loldnames' % (config.crt_lib, config.cxx_lib)
+    '-nostdlib -L %{lib} -llibc++ -l' + config.cxx_lib
 ))
 config.substitutions.append(('%{exec}',
     '%{executor} --execdir %T -- '
 ))
 
 import os, site
 site.addsitedir(os.path.join('@LIBCXX_SOURCE_DIR@', 'utils'))
 import libcxx.test.params, libcxx.test.config
 libcxx.test.config.configure(
     libcxx.test.params.DEFAULT_PARAMETERS,
     libcxx.test.features.DEFAULT_FEATURES,
     config,
     lit_config
 )