Add debug.caller() (#390)

* Add `debug.caller()`

* fix non-precompiled

src/be_debuglib.c

@@ -13,6 +13,7 @@
 #include "be_debug.h"
 #include "be_map.h"
 #include "be_vm.h"
+#include "be_exec.h"
 #include <string.h>
 
 #if BE_USE_DEBUG_MODULE
@@ -103,6 +104,26 @@ static int m_traceback(bvm *vm)
  be_return_nil(vm);
 }
 
+static int m_caller(bvm *vm)
+{
+ int depth = 1;
+ if (be_top(vm) >= 1 && be_isint(vm, 1)) {
+ depth = be_toint(vm, 1);
+ if (depth < 0) {
+ depth = -depth; /* take absolute value */
+ }
+ }
+ bcallframe *cf = (bcallframe*)be_stack_top(&vm->callstack) - depth;
+ bcallframe *base = be_stack_base(&vm->callstack);
+ if (cf >= base) {
+ bvalue *reg = be_incrtop(vm);
+ var_setval(reg, cf->func);
+ be_return(vm);
+ } else {
+ be_return_nil(vm);
+ }
+}
+
 #if BE_USE_DEBUG_HOOK
 static int m_sethook(bvm *vm)
 {
@@ -236,6 +257,7 @@ be_native_module_attr_table(debug) {
  be_native_module_function("varname", m_varname),
  be_native_module_function("upvname", m_upvname)
 #endif
+ be_native_module_function("caller", m_caller),
  be_native_module_function("gcdebug", m_gcdebug)
 };
 
@@ -252,6 +274,7 @@ module debug (scope: global, depend: BE_USE_DEBUG_MODULE) {
  top, func(m_top)
  varname, func(m_varname), BE_DEBUG_VAR_INFO
  upvname, func(m_upvname), BE_DEBUG_VAR_INFO
+ caller, func(m_caller)
  // individual counters
  allocs, func(m_allocs)
  frees, func(m_frees)

tests/debug.be

@@ -1,4 +1,29 @@
 import debug
 
 class A end
-debug.attrdump(A) #- should not crash -#
+debug.attrdump(A) #- should not crash -#
+
+# debug.caller()
+def caller_name_chain()
+ import debug
+ import introspect
+ var i = 1
+ var ret = []
+ var caller = debug.caller(i)
+ while caller
+ ret.push(introspect.name(caller))
+ i += 1
+ caller = debug.caller(i)
+ end
+ return ret
+end
+var chain = caller_name_chain()
+assert(chain[0] == 'caller_name_chain')
+
+def guess_my_name__()
+ return caller_name_chain()
+end
+chain = guess_my_name__()
+print(chain)
+assert(chain[0] == 'caller_name_chain')
+assert(chain[1] == 'guess_my_name__')