On uncaught exception, execute finally clauses and collect backtrace.

lit-test/libartiq_personality/Makefile

@@ -1,4 +1,4 @@
 CC ?= clang
 
 libartiq_personality.so: ../../soc/runtime/artiq_personality.c artiq_terminate.c
-	$(CC) -Wall -Werror -I. -I../../soc/runtime -g -fPIC -shared -o $@ $^
+	$(CC) -std=c99 -Wall -Werror -I. -I../../soc/runtime -g -fPIC -shared -o $@ $^

lit-test/libartiq_personality/artiq_terminate.c

@@ -4,11 +4,26 @@
 #include <unwind.h>
 #include <artiq_personality.h>
 
-void __artiq_terminate(struct artiq_exception *exn) {
+#define __USE_GNU
+#include <dlfcn.h>
+
+void __artiq_terminate(struct artiq_exception *exn,
+                       struct artiq_backtrace_item *backtrace,
+                       size_t backtrace_size) {
   printf("Uncaught %s: %s (%"PRIi64", %"PRIi64", %"PRIi64")\n"
          "at %s:%"PRIi32":%"PRIi32"\n",
          exn->name, exn->message,
          exn->param[0], exn->param[1], exn->param[1],
          exn->file, exn->line, exn->column + 1);
+
+  for(size_t i = 0; i < backtrace_size; i++) {
+    Dl_info info;
+    if(dladdr((void*) backtrace[i].function, &info) && info.dli_sname) {
+      printf("at %s+%p\n", info.dli_sname, (void*)backtrace[i].offset);
+    } else {
+      printf("at %p+%p\n", (void*)backtrace[i].function, (void*)backtrace[i].offset);
+    }
+  }
+
   exit(1);
 }

lit-test/test/exceptions/finally_uncaught.py

@@ -0,0 +1,12 @@
+# RUN: %not %python -m artiq.compiler.testbench.jit %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+# REQUIRES: exceptions
+
+def f():
+    try:
+        1/0
+    finally:
+        print("f-fin")
+
+# CHECK-L: f-fin
+f()

soc/runtime/artiq_personality.c

@@ -200,11 +200,17 @@ static uintptr_t readEncodedPointer(const uint8_t **data, uint8_t encoding) {
 #define ARTIQ_EXCEPTION_CLASS 0x4152545141525451LL // 'ARTQARTQ'
 
 static void __artiq_cleanup(_Unwind_Reason_Code reason, struct _Unwind_Exception *exc);
+static _Unwind_Reason_Code __artiq_uncaught_exception(
+        int version, _Unwind_Action actions, uint64_t exceptionClass,
+        struct _Unwind_Exception *exceptionObject, struct _Unwind_Context *context,
+        void *stop_parameter);
 
 struct artiq_raised_exception {
   struct _Unwind_Exception unwind;
   struct artiq_exception artiq;
   int handled;
+  struct artiq_backtrace_item backtrace[1024];
+  size_t backtrace_size;
 };
 
 static struct artiq_raised_exception inflight;
@@ -216,13 +222,17 @@ void __artiq_raise(struct artiq_exception *artiq_exn) {
   inflight.unwind.exception_class = ARTIQ_EXCEPTION_CLASS;
   inflight.unwind.exception_cleanup = &__artiq_cleanup;
   inflight.handled = 0;
+  inflight.backtrace_size = 0;
 
   _Unwind_Reason_Code result = _Unwind_RaiseException(&inflight.unwind);
   EH_ASSERT((result == _URC_END_OF_STACK) &&
             "Unexpected error during unwinding");
 
   // If we're here, there are no handlers, only cleanups.
-  __artiq_terminate(&inflight.artiq);
+  // Force unwinding anyway; we shall stop at nothing except the end of stack.
+  result = _Unwind_ForcedUnwind(&inflight.unwind, &__artiq_uncaught_exception,
+                                NULL);
+  EH_FAIL("_Unwind_ForcedUnwind should not return");
 }
 
 void __artiq_reraise() {
@@ -238,7 +248,7 @@ void __artiq_reraise() {
   }
 }
 
-/* Catching */
+/* Unwinding */
 
 // The code below does not refer to the `inflight` global.
 
@@ -250,6 +260,34 @@ static void __artiq_cleanup(_Unwind_Reason_Code reason, struct _Unwind_Exception
   memset(&inflight->artiq, 0, sizeof(struct artiq_exception));
 }
 
+static _Unwind_Reason_Code __artiq_uncaught_exception(
+        int version, _Unwind_Action actions, uint64_t exceptionClass,
+        struct _Unwind_Exception *exceptionObject, struct _Unwind_Context *context,
+        void *stop_parameter) {
+  struct artiq_raised_exception *inflight =
+          (struct artiq_raised_exception*)exceptionObject;
+  EH_ASSERT(inflight->backtrace_size <
+            sizeof(inflight->backtrace) / sizeof(inflight->backtrace[0]) &&
+            "Out of space for backtrace");
+
+  uintptr_t pc = _Unwind_GetIP(context);
+  uintptr_t funcStart = _Unwind_GetRegionStart(context);
+  uintptr_t pcOffset = pc - funcStart;
+  EH_LOG("===> uncaught (pc=%p+%p)", (void*)funcStart, (void*)pcOffset);
+
+  inflight->backtrace[inflight->backtrace_size].function = funcStart;
+  inflight->backtrace[inflight->backtrace_size].offset = pcOffset;
+  ++inflight->backtrace_size;
+
+  if(actions & _UA_END_OF_STACK) {
+    EH_LOG0("end of stack");
+    __artiq_terminate(&inflight->artiq, inflight->backtrace, inflight->backtrace_size);
+  } else {
+    EH_LOG0("continue");
+    return _URC_NO_REASON;
+  }
+}
+
 _Unwind_Reason_Code __artiq_personality(
         int version, _Unwind_Action actions, uint64_t exceptionClass,
         struct _Unwind_Exception *exceptionObject, struct _Unwind_Context *context) {

soc/runtime/artiq_personality.h

@@ -15,6 +15,11 @@ struct artiq_exception {
   int64_t param[3];
 };
 
+struct artiq_backtrace_item {
+  intptr_t function;
+  intptr_t offset;
+};
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -26,7 +31,9 @@ void __artiq_reraise()
         __attribute__((noreturn));
 
 /* Called by the runtime */
-void __artiq_terminate(struct artiq_exception *artiq_exn)
+void __artiq_terminate(struct artiq_exception *artiq_exn,
+                       struct artiq_backtrace_item *backtrace,
+                       size_t backtrace_size)
         __attribute__((noreturn));
 
 #ifdef __cplusplus