Revert "Use dwarf exceptions on i686 as well"

This reverts commit ca43ab5ccd.

It was reported in https://github.com/mstorsjo/llvm-mingw/issues/8 that
the dwarf unwinding on i686 doesn't always work.

This commit adds a testcase for the case that didn't work previously.

Dockerfile.dev

@@ -75,7 +75,7 @@ COPY test/*.cpp ./test/
 RUN cd test && \
     for arch in $TOOLCHAIN_ARCHS; do \
         mkdir -p $arch && \
-        for test in hello-cpp hello-exception tlstest-main; do \
+        for test in hello-cpp hello-exception tlstest-main exception-locale; do \
             $arch-w64-mingw32-clang++ $test.cpp -o $arch/$test.exe || exit 1; \
         done; \
         for test in tlstest-lib; do \

run-tests.sh

@@ -16,7 +16,7 @@ TESTS_C="hello hello-tls crt-test setjmp"
 TESTS_C_DLL="autoimport-lib"
 TESTS_C_LINK_DLL="autoimport-main"
 TESTS_C_NO_BUILTIN="crt-test"
-TESTS_CPP="hello-cpp hello-exception tlstest-main"
+TESTS_CPP="hello-cpp hello-exception tlstest-main exception-locale"
 TESTS_CPP_DLL="tlstest-lib"
 TESTS_SSP="ssp"
 for arch in $ARCHS; do

test/exception-locale.cpp

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2018 SquallATF
+ *
+ * This file is part of llvm-mingw.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <iostream>
+#include <typeinfo>
+
+int main(int argc, char *argv[]) {
+    try {
+        std::locale loc("test");
+    } catch (std::runtime_error& e) {
+        std::cerr << "Caught " << e.what() << std::endl;
+        std::cerr << "Type " << typeid(e).name() << std::endl;
+    } catch (...) {
+        std::cerr << "catch all" << std::endl;
+    }
+
+    return 0;
+}

wrappers/clang-target-wrapper.sh

@@ -10,8 +10,13 @@ esac
 ARCH=$(echo $TARGET | sed 's/-.*//')
 case $ARCH in
 i686)
-    # Dwarf is the default here.
+    # Dwarf is the default for i686, but libunwind sometimes fails to
-    ARCH_FLAGS=
+    # to unwind correctly on i686. This issue might be related to cases
+    # of DW_CFA_GNU_args_size (which were adjusted in libunwind SVN r337312).
+    # The issue can be reproduced with test/exception-locale.cpp.
+    # The issue goes away if building libunwind/libcxxabi/libcxx and the
+    # test example with -mstack-alignment=16 -mstackrealign.
+    ARCH_FLAGS=-fsjlj-exceptions
     ;;
 x86_64)
     # SEH is the default here.