Reland "Enable `-funwind-tables` flag when building libunwind"

Summary:
Relands https://reviews.llvm.org/D70815.

The original commit set `CMAKE_TRY_COMPILE_TARGET_TYPE` to
`STATIC_LIBRARY` globally in libunwind/CMakeLists.txt, which effectively
disabled the linking step in CMake checks.

This broke some builds (see 938c70b86c7d2165f8c28d5700e9c1ac1263307e).

Here we set CMAKE_TRY_COMPILE_TARGET_TYPE to
STATIC_LIBRARY only when checking for presence of the `-funwind-tables`
flag, and then set it back to the original value so it doesn't affect
other checks.

Reviewers: mstorsjo, jfb

Subscribers: mgorny, christof, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D71117

4 files changed, 14 insertions, 2 deletions

diff --git a/libunwind/test/CMakeLists.txt b/libunwind/test/CMakeLists.txt
index d902e3e8294..40d4acd4e8c 100644
--- a/libunwind/test/CMakeLists.txt
+++ b/libunwind/test/CMakeLists.txt
@@ -16,6 +16,7 @@ pythonize_bool(LIBCXX_ENABLE_SHARED)
 pythonize_bool(LIBUNWIND_ENABLE_SHARED)
 pythonize_bool(LIBUNWIND_ENABLE_THREADS)
 pythonize_bool(LIBUNWIND_ENABLE_EXCEPTIONS)
+pythonize_bool(LIBUNWIND_USES_ARM_EHABI)
 pythonize_bool(LIBUNWIND_USE_COMPILER_RT)
 pythonize_bool(LIBUNWIND_BUILD_EXTERNAL_THREAD_LIBRARY)
 set(LIBUNWIND_TARGET_INFO "libcxx.test.target_info.LocalTI" CACHE STRING
diff --git a/libunwind/test/libunwind/test/config.py b/libunwind/test/libunwind/test/config.py
index 05e3f3cc21f..41ca3f9b4a4 100644
--- a/libunwind/test/libunwind/test/config.py
+++ b/libunwind/test/libunwind/test/config.py
@@ -37,6 +37,8 @@ class Configuration(LibcxxConfiguration):
         super(Configuration, self).configure_features()
         if not self.get_lit_bool('enable_exceptions', True):
             self.config.available_features.add('libcxxabi-no-exceptions')
+        if self.get_lit_bool('arm_ehabi', False):
+            self.config.available_features.add('libunwind-arm-ehabi')
 
     def configure_compile_flags(self):
         self.cxx.compile_flags += ['-DLIBUNWIND_NO_TIMER']
@@ -66,3 +68,11 @@ class Configuration(LibcxxConfiguration):
 
     def configure_compile_flags_rtti(self):
         pass
+
+    def configure_link_flags_cxx_library(self):
+        # libunwind tests should not link with libc++
+        pass
+
+    def configure_link_flags_abi_library(self):
+        # libunwind tests should not link with libc++abi
+        pass
diff --git a/libunwind/test/lit.site.cfg.in b/libunwind/test/lit.site.cfg.in
index 34da72ac106..37f90a90efd 100644
--- a/libunwind/test/lit.site.cfg.in
+++ b/libunwind/test/lit.site.cfg.in
@@ -19,6 +19,7 @@ config.executor                 = "@LIBUNWIND_EXECUTOR@"
 config.libunwind_shared         = @LIBUNWIND_ENABLE_SHARED@
 config.enable_shared            = @LIBCXX_ENABLE_SHARED@
 config.enable_exceptions        = @LIBUNWIND_ENABLE_EXCEPTIONS@
+config.arm_ehabi                = @LIBUNWIND_USES_ARM_EHABI@
 config.host_triple              = "@LLVM_HOST_TRIPLE@"
 config.target_triple            = "@TARGET_TRIPLE@"
 config.use_target               = bool("@LIBUNWIND_TARGET_TRIPLE@")
diff --git a/libunwind/test/signal_frame.pass.cpp b/libunwind/test/signal_frame.pass.cpp
index a6f3f483bea..a899461fafb 100644
--- a/libunwind/test/signal_frame.pass.cpp
+++ b/libunwind/test/signal_frame.pass.cpp
@@ -9,6 +9,8 @@
 
 // Ensure that functions marked as signal frames are reported as such.
 
+// UNSUPPORTED: libunwind-arm-ehabi
+
 #include <assert.h>
 #include <stdlib.h>
 #include <libunwind.h>
@@ -20,9 +22,7 @@ void test() {
   unw_getcontext(&uc);
   unw_init_local(&cursor, &uc);
   assert(unw_step(&cursor) > 0);
-#if !defined(_LIBUNWIND_ARM_EHABI)
   assert(unw_is_signal_frame(&cursor));
-#endif
 }
 
 int main() {