YCF: better debug support for checking nested yielding functions

Add support for checking for pointers to any of the stack frames
belonging to nested yielding functions.

5 files changed, 58 insertions, 9 deletions

diff --git a/erts/lib_src/yielding_c_fun/README.md b/erts/lib_src/yielding_c_fun/README.md
index 2cba57a3e8..b57c2847bc 100644
--- a/erts/lib_src/yielding_c_fun/README.md
+++ b/erts/lib_src/yielding_c_fun/README.md
@@ -145,7 +145,7 @@ Usage: yielding_c_fun [-h]
 
 * `-fexternal function_name`
 
-  YCF expects that a yielding verison of the function called
+  YCF expects that a yielding version of the function called
   `function_name` is generated externally. Calls to the function
   called `function_name` from yielding functions calls the externally
   generated yielding version of the function called `function_name`.
@@ -167,6 +167,30 @@ Usage: yielding_c_fun [-h]
   to data that is allocated on the call stack. The program crashes
   with an error message if any such pointer is found.
 
+  The generated debug code depends on that a function called
+  `ycf_debug_get_stack_start()` is declared somewhere in the
+  program. The `ycf_debug_get_stack_start()` functions should return a
+  value of type `void*`. Example:
+  
+          static _Thread_local void* ycf_debug_global_stack_start_ptr = NULL;
+          void* ycf_debug_get_stack_start() {
+              return ycf_debug_global_stack_start_ptr;
+          }
+  
+  If `ycf_debug_get_stack_start()` returns `NULL`, the value of the
+  `ycf_yield_state` parameter will be used as the start of the stack (it
+  is assumed that the stack grows towards lower addresses). If
+  `ycf_debug_get_stack_start()` returns something different than `NULL`,
+  that value will be used as the start of the stack. To check that
+  nested yielding functions do not have pointers to the call stack,
+  one have to make sure that `ycf_debug_get_stack_start()` returns
+  something different than `NULL` (otherwise, each function will just
+  check for pointers to its own frame). Example:
+  
+          ycf_debug_global_stack_start_ptr = &wb;
+          ret = fun_ycf_gen_yielding(&nr_of_reductions,&wb,NULL,allocator,freer,NULL,0,NULL,1);
+          ycf_debug_global_stack_start_ptr = NULL;
+
 * `-only_yielding_funs`
 
   Print only the generated functions and struct declarations. The
diff --git a/erts/lib_src/yielding_c_fun/test/examples/debug_ptr_to_stack.c b/erts/lib_src/yielding_c_fun/test/examples/debug_ptr_to_stack.c
index 76d500de24..cda48d8b2e 100644
--- a/erts/lib_src/yielding_c_fun/test/examples/debug_ptr_to_stack.c
+++ b/erts/lib_src/yielding_c_fun/test/examples/debug_ptr_to_stack.c
@@ -1,6 +1,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+void* ycf_debug_global_stack_top_ptr = NULL;
+void* ycf_debug_get_stack_start(){
+    return ycf_debug_global_stack_top_ptr;
+}
+
 #define YCF_YIELD()
 
 int fun(){
diff --git a/erts/lib_src/yielding_c_fun/test/examples/test_only_output_yielding_funs_ptr_to_stack.c b/erts/lib_src/yielding_c_fun/test/examples/test_only_output_yielding_funs_ptr_to_stack.c
index 66ed83858f..78973496e8 100644
--- a/erts/lib_src/yielding_c_fun/test/examples/test_only_output_yielding_funs_ptr_to_stack.c
+++ b/erts/lib_src/yielding_c_fun/test/examples/test_only_output_yielding_funs_ptr_to_stack.c
@@ -1,25 +1,38 @@
+
 #include <stdio.h>
 #include <stdlib.h>
 
+void* ycf_debug_global_stack_start_ptr = NULL;
+void* ycf_debug_get_stack_start(){
+    return ycf_debug_global_stack_start_ptr;
+}
 #define YCF_YIELD()
 
-int empty_fun(){
-  return 1;
+int fun2(char* to_stack_in_other_fun){
+    char value = *to_stack_in_other_fun;
+    YCF_YIELD();
+    if (value == 42) {
+        return 1;
+    } else {
+        return 0;
+    }
 }
 
 #include "tmp.ycf.h"
 
 static int fun(char x){
-  char array[10];
-  array[4] = 42;
-  char *to_stack = &array[4];
+  char array[1];
+  array[0] = 42;
+  char *to_stack = &array[0];
   x = x + 1; /* x == 2*/
-  YCF_YIELD();
   printf("ptr to: %d", (int)(*to_stack));
   x = x + 1; /* x == 3*/
   {
-  int hej = !!empty_fun();
-  return x + hej;
+      int hej = 0;
+      hej = fun2(to_stack);
+      YCF_YIELD();
+      to_stack = NULL;
+      return x + hej;
   }
 }
 
@@ -43,7 +56,9 @@ int main( int argc, const char* argv[] )
   (void)fun;
 #ifdef YCF_YIELD_CODE_GENERATED
   do{
+    ycf_debug_global_stack_start_ptr = &wb;
     ret = fun_ycf_gen_yielding(&nr_of_reductions,&wb,NULL,allocator,freer,NULL,0,NULL,1);
+    ycf_debug_global_stack_start_ptr = NULL;
     if(wb != NULL){
       printf("TRAPPED\n");
     }
diff --git a/erts/lib_src/yielding_c_fun/test/test.sh b/erts/lib_src/yielding_c_fun/test/test.sh
index e380d040b5..e1b392d969 100755
--- a/erts/lib_src/yielding_c_fun/test/test.sh
+++ b/erts/lib_src/yielding_c_fun/test/test.sh
@@ -166,6 +166,7 @@ yielding_c_fun.bin $GC $RR -yield \
                            -debug \
                            -only_yielding_funs \
                            -fnoauto fun \
+                           -fnoauto fun2 \
                            -output_file_name $TMP_INC_FILE \
                            "$DIR/examples/test_only_output_yielding_funs_ptr_to_stack.c"
 $CC $CC_ARGS -I "$TMP_DIR" "$DIR/examples/test_only_output_yielding_funs_ptr_to_stack.c"  -o $TMP_CC_OUT
diff --git a/erts/lib_src/yielding_c_fun/ycf_yield_fun.c b/erts/lib_src/yielding_c_fun/ycf_yield_fun.c
index 286a13cabf..8f3fe94441 100644
--- a/erts/lib_src/yielding_c_fun/ycf_yield_fun.c
+++ b/erts/lib_src/yielding_c_fun/ycf_yield_fun.c
@@ -870,9 +870,13 @@ void ast_add_yield_code_generated_define(ycf_node* source_out_tree/*Will be chan
      "  return bottom();\n"
      "  }\n"
      "}\n"
+     "void* ycf_debug_get_stack_start();\n"
      "#include <signal.h>\n"
      "static void ycf_debug_check_block(char* struct_name, void* stack_start, void* stack_end, void* block, size_t block_size) {\n"
      "  char* p;\n"
+     "  if (ycf_debug_get_stack_start() != NULL) {\n"
+     "    stack_end = ycf_debug_get_stack_start();\n"
+     "  }\n"
      "  for (p = block; p < (((char*)block) + block_size); p += sizeof(void*)) {\n"
      "    if(*((char**)p) > (char*)stack_start && *((char**)p) <= (char*)stack_end){\n"
      "      fprintf(stderr, \"Pointer to stack in yielded functions state!!!!! (pointer_address=%p, pointer_value=%p, struct %s,offset=%lu)\\n\", (void*)p, *((void**)p), struct_name, (unsigned long)(p-(size_t)block));\n"