Add safe tracing interface

include/cpptrace/cpptrace.hpp

@@ -26,6 +26,7 @@ namespace cpptrace {
 
     struct CPPTRACE_EXPORT raw_trace {
         std::vector<frame_ptr> frames;
+        static raw_trace from_buffer(frame_ptr* buffer, std::size_t size);
         static raw_trace current(std::uint_least32_t skip = 0);
         static raw_trace current(std::uint_least32_t skip, std::uint_least32_t max_depth);
         object_trace resolve_object_trace() const;
@@ -124,6 +125,18 @@ namespace cpptrace {
     CPPTRACE_EXPORT stacktrace generate_trace(std::uint_least32_t skip = 0);
     CPPTRACE_EXPORT stacktrace generate_trace(std::uint_least32_t skip, std::uint_least32_t max_depth);
 
+    CPPTRACE_EXPORT std::size_t safe_generate_raw_trace(
+        frame_ptr* buffer,
+        std::size_t size,
+        std::uint_least32_t skip = 0
+    );
+    CPPTRACE_EXPORT std::size_t safe_generate_raw_trace(
+        frame_ptr* buffer,
+        std::size_t size,
+        std::uint_least32_t skip,
+        std::uint_least32_t max_depth
+    );
+
     // utilities:
     CPPTRACE_EXPORT std::string demangle(const std::string& name);
     CPPTRACE_EXPORT void absorb_trace_exceptions(bool absorb);

src/cpptrace.cpp

@@ -28,6 +28,11 @@
 #define CYAN    ESC "36m"
 
 namespace cpptrace {
+    CPPTRACE_FORCE_NO_INLINE
+    raw_trace raw_trace::from_buffer(frame_ptr* buffer, std::size_t size) {
+        return raw_trace{std::vector<cpptrace::frame_ptr>(buffer, buffer + size)};
+    }
+
     CPPTRACE_FORCE_NO_INLINE
     raw_trace raw_trace::current(std::uint_least32_t skip) {
         return generate_raw_trace(skip + 1);
@@ -263,6 +268,21 @@ namespace cpptrace {
         }
     }
 
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_generate_raw_trace(frame_ptr* buffer, std::size_t size, std::uint_least32_t skip) {
+        return detail::safe_capture_frames(buffer, size, skip + 1, UINT_LEAST32_MAX);
+    }
+
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_generate_raw_trace(
+         frame_ptr* buffer,
+         std::size_t size,
+         std::uint_least32_t skip,
+         std::uint_least32_t max_depth
+    ) {
+        return detail::safe_capture_frames(buffer, size, skip + 1, max_depth);
+    }
+
     CPPTRACE_FORCE_NO_INLINE
     object_trace generate_object_trace(std::uint_least32_t skip) {
         try {

src/unwind/unwind.hpp

@@ -14,8 +14,12 @@ namespace detail {
     #else
     constexpr std::size_t hard_max_frames = 100;
     #endif
+
     CPPTRACE_FORCE_NO_INLINE
     std::vector<frame_ptr> capture_frames(std::size_t skip, std::size_t max_depth);
+
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_capture_frames(frame_ptr* buffer, std::size_t size, std::size_t skip, std::size_t max_depth);
 }
 }
 

src/unwind/unwind_with_dbghelp.cpp

@@ -152,6 +152,12 @@ namespace detail {
         }
         return trace;
     }
+
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_capture_frames(frame_ptr* buffer, std::size_t size, std::size_t skip, std::size_t max_depth) {
+        // Can't safe trace with dbghelp
+        return 0;
+    }
     #if IS_MSVC
     #pragma warning(pop)
     #endif

src/unwind/unwind_with_execinfo.cpp

@@ -27,6 +27,12 @@ namespace detail {
         }
         return frames;
     }
+
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_capture_frames(frame_ptr* buffer, std::size_t size, std::size_t skip, std::size_t max_depth) {
+        // Can't safe trace with execinfo
+        return 0;
+    }
 }
 }
 

src/unwind/unwind_with_libunwind.cpp

@@ -36,6 +36,41 @@ namespace detail {
         } while(unw_step(&cursor) > 0 && frames.size() < max_depth);
         return frames;
     }
+
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_capture_frames(frame_ptr* buffer, std::size_t size, std::size_t skip, std::size_t max_depth) {
+        // some code duplication, but whatever
+        skip++;
+        std::vector<frame_ptr> frames;
+        unw_context_t context;
+        unw_cursor_t cursor;
+        // thread and signal-safe https://www.nongnu.org/libunwind/man/unw_getcontext(3).html
+        unw_getcontext(&context);
+        // thread and signal-safe https://www.nongnu.org/libunwind/man/unw_init_local(3).html
+        unw_init_local(&cursor, &context);
+        size_t i = 0;
+        while(i < size && i < max_depth) {
+            unw_word_t pc;
+            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);
+            unw_get_reg(&cursor, UNW_REG_SP, &sp);
+            if(skip) {
+                skip--;
+            } else {
+                // pc is the instruction after the `call`, adjust back to the previous instruction
+                // just a cast, signal safe
+                buffer[i] = to_frame_ptr(pc) - 1;
+                i++;
+            }
+            // thread and signal-safe as long as the cursor is in the local address space, which it is
+            // https://www.nongnu.org/libunwind/man/unw_step(3).html
+            if(unw_step(&cursor) <= 0) {
+                break;
+            }
+        }
+        return i;
+    }
 }
 }
 

src/unwind/unwind_with_nothing.cpp

@@ -10,6 +10,11 @@ namespace detail {
     std::vector<frame_ptr> capture_frames(std::size_t, std::size_t) {
         return {};
     }
+
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_capture_frames(frame_ptr* buffer, std::size_t size, std::size_t skip, std::size_t max_depth) {
+        return 0;
+    }
 }
 }
 

src/unwind/unwind_with_unwind.cpp

@@ -62,6 +62,12 @@ namespace detail {
         frames.shrink_to_fit();
         return frames;
     }
+
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_capture_frames(frame_ptr* buffer, std::size_t size, std::size_t skip, std::size_t max_depth) {
+        // Can't safe trace with _Unwind
+        return 0;
+    }
 }
 }
 

src/unwind/unwind_with_winapi.cpp

@@ -37,6 +37,12 @@ namespace detail {
         }
         return frames;
     }
+
+    CPPTRACE_FORCE_NO_INLINE
+    std::size_t safe_capture_frames(frame_ptr* buffer, std::size_t size, std::size_t skip, std::size_t max_depth) {
+        // Can't safe trace with winapi
+        return 0;
+    }
 }
 }