[Tarantool-patches] [PATCH luajit v2 2/6] OSX: Fix build by hardcoding external frame unwinding.

[Maksim Kokryashkin]

Apparently they can't even get 'grep' right, let alone a keyboard.

(cherry picked from commit d4a554d6ee1507f7313641b26ed09bf1b518fa1f)

MacOS uses BSD grep, which is slightly different from GNU grep.
Because of that, the shell script determining whether external
unwinding is possible doesn't work right.

External unwinding is possible on MacOS, so this patch enables
it by default.

Maxim Kokryashkin:
* added the description for the problem

Needed for tarantool/tarantool#6096
Needed for tarantool/tarantool#7230
---
>I have two questions below and also there’s no mentioning in the message that
>you removes the non-GC64 workflow for the Darwin platform. Why is it done
>at all? Previous commit just mentioned that GC64 is enabled by default.
My bad! As Sergey mentioned, we needed to clarify that it is not only
enabled by default, it is now forbidden to run on MacOS in non-GC64
mode. Also, I moved those changes to the first patch, because it is
more logical in terms of structure.

>1. how is it relvant to grep??
>
>> include:
>> - BUILDTYPE: Debug
>> CMAKEFLAGS: -DCMAKE_BUILD_TYPE=Debug -DLUA_USE_ASSERT=ON -DLUA_USE_APICHECK=ON
>> @@ -69,15 +69,6 @@ jobs:
>> - name: test
>> run: cmake --build . --parallel --target test
>>
>> - test-tarantool-debug-wo-GC64:
>> - name: Tarantool Debug GC64:OFF
>> - needs: test-luajit
>> - uses: tarantool/tarantool/.github/workflows/luajit-integration.yml at master
>> - with:
>> - GC64: OFF
>> - buildtype: Debug
>> - host: macos-11
>> - revision: ${{ github.sha }}
>
>(1)
>
>> test-tarantool-debug-w-GC64:
>> name: Tarantool Debug GC64:ON
>> needs: test-luajit
>> @@ -87,15 +78,6 @@ jobs:
>> buildtype: Debug
>> host: macos-11
>> revision: ${{ github.sha }}
>> - test-tarantool-release-wo-GC64:
>> - name: Tarantool Release GC64:OFF
>> - needs: test-luajit
>> - uses: tarantool/tarantool/.github/workflows/luajit-integration.yml at master
>> - with:
>> - GC64: OFF
>> - buildtype: RelWithDebInfo
>> - host: macos-11
>> - revision: ${{ github.sha }}
>(1)
It is not relevant to grep in any way, see the comment above.

>> - COMMAND bash -c "exec 2>/dev/null; echo 'extern void b(void);int a(void){b();return 0;}' | ${CMAKE_C_COMPILER} -c -x c - -o tmpunwind.o && grep -qa -e eh_frame -e __unwind_info tmpunwind.o && echo E; rm -f tmpunwind.o"
>
>2. I don’t see any changes to the grep operation here and below - does the cherry-pick message is relevant at all?
Yes, there are no changes to grep, we just enable the external
unwinding on every Darwin system without any checks at all,
because of the issue with grep.
It is reliable, because, clang always generates unwind tables.

 cmake/SetTargetFlags.cmake | 28 ++++++++++++++++------------
 src/Makefile.original      | 15 ++++++++-------
 2 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/cmake/SetTargetFlags.cmake b/cmake/SetTargetFlags.cmake
index 36896aff..a5a3407f 100644
--- a/cmake/SetTargetFlags.cmake
+++ b/cmake/SetTargetFlags.cmake
@@ -15,18 +15,22 @@ endif()
 LuaJITTestArch(TESTARCH "${TARGET_C_FLAGS}")
 LuaJITArch(LUAJIT_ARCH "${TESTARCH}")

-string(FIND ${TARGET_C_FLAGS} "LJ_NO_UNWIND 1" UNWIND_POS)
-if(UNWIND_POS EQUAL -1)
-  execute_process(
-    COMMAND bash -c "exec 2>/dev/null; echo 'extern void b(void);int a(void){b();return 0;}' | ${CMAKE_C_COMPILER} -c -x c - -o tmpunwind.o && grep -qa -e eh_frame -e __unwind_info tmpunwind.o && echo E; rm -f tmpunwind.o"
-    WORKING_DIRECTORY ${LUAJIT_SOURCE_DIR}
-    OUTPUT_VARIABLE TESTUNWIND
-    RESULT_VARIABLE TESTUNWIND_RC
-  )
-  if(TESTUNWIND_RC EQUAL 0)
-    string(FIND "${TESTUNWIND}" "E" UNW_TEST_POS)
-    if(NOT UNW_TEST_POS EQUAL -1)
-      AppendFlags(TARGET_C_FLAGS -DLUAJIT_UNWIND_EXTERNAL)
+if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+  AppendFlags(TARGET_C_FLAGS -DLUAJIT_UNWIND_EXTERNAL)
+else()
+  string(FIND ${TARGET_C_FLAGS} "LJ_NO_UNWIND 1" UNWIND_POS)
+  if(UNWIND_POS EQUAL -1)
+    execute_process(
+      COMMAND bash -c "exec 2>/dev/null; echo 'extern void b(void);int a(void){b();return 0;}' | ${CMAKE_C_COMPILER} -c -x c - -o tmpunwind.o && grep -qa -e eh_frame -e __unwind_info tmpunwind.o && echo E; rm -f tmpunwind.o"
+      WORKING_DIRECTORY ${LUAJIT_SOURCE_DIR}
+      OUTPUT_VARIABLE TESTUNWIND
+      RESULT_VARIABLE TESTUNWIND_RC
+    )
+    if(TESTUNWIND_RC EQUAL 0)
+      string(FIND "${TESTUNWIND}" "E" UNW_TEST_POS)
+      if(NOT UNW_TEST_POS EQUAL -1)
+        AppendFlags(TARGET_C_FLAGS -DLUAJIT_UNWIND_EXTERNAL)
+      endif()
     endif()
   endif()
 endif()
diff --git a/src/Makefile.original b/src/Makefile.original
index c9609700..d1373b40 100644
--- a/src/Makefile.original
+++ b/src/Makefile.original
@@ -320,18 +320,12 @@ else
 ifeq (,$(shell $(TARGET_CC) -o /dev/null -c -x c /dev/null -fno-stack-protector 2>/dev/null || echo 1))
   TARGET_XCFLAGS+= -fno-stack-protector
 endif
-ifeq (,$(findstring LJ_NO_UNWIND 1,$(TARGET_TESTARCH)))
-  # Find out whether the target toolchain always generates unwind tables.
-  TARGET_TESTUNWIND=$(shell exec 2>/dev/null; echo 'extern void b(void);int a(void){b();return 0;}' | $(TARGET_CC) -c -x c - -o tmpunwind.o && grep -qa -e eh_frame -e __unwind_info tmpunwind.o && echo E; rm -f tmpunwind.o)
-  ifneq (,$(findstring E,$(TARGET_TESTUNWIND)))
-    TARGET_XCFLAGS+= -DLUAJIT_UNWIND_EXTERNAL
-  endif
-endif
 ifeq (Darwin,$(TARGET_SYS))
   ifeq (,$(MACOSX_DEPLOYMENT_TARGET))
     export MACOSX_DEPLOYMENT_TARGET=10.4
   endif
   TARGET_STRIP+= -x
+  TARGET_XCFLAGS+= -DLUAJIT_UNWIND_EXTERNAL
   TARGET_XSHLDFLAGS= -dynamiclib -single_module -undefined dynamic_lookup -fPIC
   TARGET_DYNXLDOPTS=
   TARGET_XSHLDFLAGS+= -install_name $(TARGET_DYLIBPATH) -compatibility_version $(MAJVER).$(MINVER) -current_version $(MAJVER).$(MINVER).$(RELVER)
@@ -345,6 +339,13 @@ ifeq (iOS,$(TARGET_SYS))
     TARGET_XCFLAGS+= -fno-omit-frame-pointer
   endif
 else
+  ifeq (,$(findstring LJ_NO_UNWIND 1,$(TARGET_TESTARCH)))
+    # Find out whether the target toolchain always generates unwind tables.
+    TARGET_TESTUNWIND=$(shell exec 2>/dev/null; echo 'extern void b(void);int a(void){b();return 0;}' | $(TARGET_CC) -c -x c - -o tmpunwind.o && grep -qa -e eh_frame -e __unwind_info tmpunwind.o && echo E; rm -f tmpunwind.o)
+    ifneq (,$(findstring E,$(TARGET_TESTUNWIND)))
+      TARGET_XCFLAGS+= -DLUAJIT_UNWIND_EXTERNAL
+    endif
+  endif
   ifneq (SunOS,$(TARGET_SYS))
     ifneq (PS3,$(TARGET_SYS))
       TARGET_XLDFLAGS+= -Wl,-E
--
2.32.1 (Apple Git-133)