4 files changed, 48 insertions, 27 deletions

diff --git a/src/common/common_funcs.h b/src/common/common_funcs.h
index 71b64e32a..4ace2cd33 100644
--- a/src/common/common_funcs.h
+++ b/src/common/common_funcs.h
@@ -52,9 +52,13 @@ __declspec(dllimport) void __stdcall DebugBreak(void);
 // Generic function to get last error message.
 // Call directly after the command or use the error num.
 // This function might change the error code.
-// Defined in Misc.cpp.
+// Defined in misc.cpp.
 [[nodiscard]] std::string GetLastErrorMsg();
 
+// Like GetLastErrorMsg(), but passing an explicit error code.
+// Defined in misc.cpp.
+[[nodiscard]] std::string NativeErrorToString(int e);
+
 #define DECLARE_ENUM_FLAG_OPERATORS(type)                                                          \
     [[nodiscard]] constexpr type operator|(type a, type b) noexcept {                              \
         using T = std::underlying_type_t<type>;                                                    \
diff --git a/src/common/fiber.cpp b/src/common/fiber.cpp
index 3c1eefcb7..39532ff58 100644
--- a/src/common/fiber.cpp
+++ b/src/common/fiber.cpp
@@ -116,16 +116,19 @@ void Fiber::Rewind() {
     boost::context::detail::jump_fcontext(impl->rewind_context, this);
 }
 
-void Fiber::YieldTo(std::shared_ptr<Fiber> from, std::shared_ptr<Fiber> to) {
-    ASSERT_MSG(from != nullptr, "Yielding fiber is null!");
-    ASSERT_MSG(to != nullptr, "Next fiber is null!");
-    to->impl->guard.lock();
-    to->impl->previous_fiber = from;
-    auto transfer = boost::context::detail::jump_fcontext(to->impl->context, to.get());
-    ASSERT(from->impl->previous_fiber != nullptr);
-    from->impl->previous_fiber->impl->context = transfer.fctx;
-    from->impl->previous_fiber->impl->guard.unlock();
-    from->impl->previous_fiber.reset();
+void Fiber::YieldTo(std::weak_ptr<Fiber> weak_from, Fiber& to) {
+    to.impl->guard.lock();
+    to.impl->previous_fiber = weak_from.lock();
+
+    auto transfer = boost::context::detail::jump_fcontext(to.impl->context, &to);
+
+    // "from" might no longer be valid if the thread was killed
+    if (auto from = weak_from.lock()) {
+        ASSERT(from->impl->previous_fiber != nullptr);
+        from->impl->previous_fiber->impl->context = transfer.fctx;
+        from->impl->previous_fiber->impl->guard.unlock();
+        from->impl->previous_fiber.reset();
+    }
 }
 
 std::shared_ptr<Fiber> Fiber::ThreadToFiber() {
diff --git a/src/common/fiber.h b/src/common/fiber.h
index f7f587f8c..f2a8ff29a 100644
--- a/src/common/fiber.h
+++ b/src/common/fiber.h
@@ -41,7 +41,7 @@ public:
 
     /// Yields control from Fiber 'from' to Fiber 'to'
     /// Fiber 'from' must be the currently running fiber.
-    static void YieldTo(std::shared_ptr<Fiber> from, std::shared_ptr<Fiber> to);
+    static void YieldTo(std::weak_ptr<Fiber> weak_from, Fiber& to);
     [[nodiscard]] static std::shared_ptr<Fiber> ThreadToFiber();
 
     void SetRewindPoint(std::function<void(void*)>&& rewind_func, void* rewind_param);
diff --git a/src/common/misc.cpp b/src/common/misc.cpp
index 1d5393597..495385b9e 100644
--- a/src/common/misc.cpp
+++ b/src/common/misc.cpp
@@ -12,27 +12,41 @@
 
 #include "common/common_funcs.h"
 
-// Generic function to get last error message.
-// Call directly after the command or use the error num.
-// This function might change the error code.
-std::string GetLastErrorMsg() {
-    static constexpr std::size_t buff_size = 255;
-    char err_str[buff_size];
-
+std::string NativeErrorToString(int e) {
 #ifdef _WIN32
-    FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM, nullptr, GetLastError(),
-                   MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), err_str, buff_size, nullptr);
-    return std::string(err_str, buff_size);
-#elif defined(__GLIBC__) && (_GNU_SOURCE || (_POSIX_C_SOURCE < 200112L && _XOPEN_SOURCE < 600))
+    LPSTR err_str;
+
+    DWORD res = FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                                   FORMAT_MESSAGE_IGNORE_INSERTS,
+                               nullptr, e, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                               reinterpret_cast<LPSTR>(&err_str), 1, nullptr);
+    if (!res) {
+        return "(FormatMessageA failed to format error)";
+    }
+    std::string ret(err_str);
+    LocalFree(err_str);
+    return ret;
+#else
+    char err_str[255];
+#if defined(__GLIBC__) && (_GNU_SOURCE || (_POSIX_C_SOURCE < 200112L && _XOPEN_SOURCE < 600))
     // Thread safe (GNU-specific)
-    const char* str = strerror_r(errno, err_str, buff_size);
+    const char* str = strerror_r(e, err_str, sizeof(err_str));
     return std::string(str);
 #else
     // Thread safe (XSI-compliant)
-    const int success = strerror_r(errno, err_str, buff_size);
-    if (success != 0) {
-        return {};
+    int second_err = strerror_r(e, err_str, sizeof(err_str));
+    if (second_err != 0) {
+        return "(strerror_r failed to format error)";
     }
     return std::string(err_str);
+#endif // GLIBC etc.
+#endif // _WIN32
+}
+
+std::string GetLastErrorMsg() {
+#ifdef _WIN32
+    return NativeErrorToString(GetLastError());
+#else
+    return NativeErrorToString(errno);
 #endif
 }