Improve libunwind support on macos and test in ci (#315)

Author: jeremy-rifkin

ci/test-all-configs.py

@@ -393,6 +393,7 @@ def run_macos_matrix(compilers: list, shared: bool):
             "unwind": [
                 "CPPTRACE_UNWIND_WITH_EXECINFO",
                 "CPPTRACE_UNWIND_WITH_UNWIND",
+                "CPPTRACE_UNWIND_WITH_LIBUNWIND",
                 #"CPPTRACE_UNWIND_WITH_NOTHING",
             ],
             "symbols": [

src/unwind/unwind_with_libunwind.cpp

@@ -12,6 +12,18 @@
 
 #include <libunwind.h>
 
+namespace {
+// Strip pointer authentication code from an instruction address.
+// Apple's unw_get_reg(UNW_REG_IP) may return PAC-signed addresses with signature bits in
+// the upper bytes.
+inline uintptr_t depaci(uintptr_t pc) {
+    #if defined(__APPLE__) && (defined(__arm64__) || defined(__aarch64__))
+     __asm__ volatile("xpaci %0" : "+r"(pc));
+    #endif
+    return pc;
+}
+}
+
 CPPTRACE_BEGIN_NAMESPACE
 namespace detail {
     CPPTRACE_FORCE_NO_INLINE
@@ -26,6 +38,7 @@ namespace detail {
             unw_word_t pc;
             unw_word_t sp;
             unw_get_reg(&cursor, UNW_REG_IP, &pc);
+            pc = depaci(pc);
             unw_get_reg(&cursor, UNW_REG_SP, &sp);
             if(skip) {
                 skip--;
@@ -53,6 +66,7 @@ namespace detail {
             unw_word_t sp;
             // thread and signal-safe https://www.nongnu.org/libunwind/man/unw_get_reg(3).html
             unw_get_reg(&cursor, UNW_REG_IP, &pc);
+            pc = depaci(pc);
             unw_get_reg(&cursor, UNW_REG_SP, &sp);
             if(skip) {
                 skip--;