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[Go] Adjust last patch to avoid write-after-write data race on global

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variable.  Only set the variable if another global variable is true,
but that variable is always false.  The effect is that the variable is
never written, but as far as the compiler is concerned it might escape.
This commit is contained in:
Ian Lance Taylor 2014-10-14 10:05:43 -07:00
commit 0577ff2220
2 changed files with 41 additions and 14 deletions
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45
Source/Modules/go.cxx
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@ -920,15 +920,8 @@ private:
needs_wrapper = true;
}
// If the parameter has an argout or freearg typemap, we need to
// make sure that it escapes, in case it contains any pointers.
if (Getattr(p, "tmap:argout") || Getattr(p, "tmap:freearg")) {
if (!goTypeIsInterface(p, Getattr(p, "type"))) {
String *tm = goWrapperType(p, Getattr(p, "type"), false);
Printf(f_go_wrappers, "var %s_escape_%d %s\n", wname, i, tm);
Delete(tm);
needs_wrapper = true;
}
if (paramNeedsEscape(p)) {
needs_wrapper = true;
}
p = nextParm(p);
@ -1218,11 +1211,10 @@ private:
// If the parameter has an argout or freearg typemap, make
// sure that it escapes.
if (Getattr(p, "tmap:argout") || Getattr(p, "tmap:freearg")) {
// No need to do anything for C++ class type.
if (!goTypeIsInterface(p, pt)) {
Printf(f_go_wrappers, "\t%s_escape_%d = %s\n", wname, i, Getattr(p, "emit:goinput"));
}
if (paramNeedsEscape(p)) {
Printv(f_go_wrappers, "\tif Swig_escape_always_false {\n", NULL);
Printv(f_go_wrappers, "\t\tSwig_escape_val = ", Getattr(p, "emit:goinput"), "\n", NULL);
Printv(f_go_wrappers, "\t}\n", NULL);
}
p = nextParm(p);
@ -1291,6 +1283,31 @@ private:
return "base";
}
/* ----------------------------------------------------------------------
* paramNeedsEscape()
*
* A helper for goFunctionWrapper that returns whether a parameter
* needs to explicitly escape. This is true if the parameter has a
* non-empty argout or freearg typemap, because in those cases the
* Go argument might be or contain a pointer. We need to ensure
* that that pointer does not oint into the stack, which means that
* it needs to escape.
* ---------------------------------------------------------------------- */
bool paramNeedsEscape(Parm *p) {
String *argout = Getattr(p, "tmap:argout");
String *freearg = Getattr(p, "tmap:freearg");
if ((!argout || Len(argout) == 0) && (!freearg || Len(freearg) == 0)) {
return false;
}
// If a C++ type is represented as an interface type in Go, then
// we don't care whether it escapes, because we know that the
// pointer is a C++ pointer.
if (goTypeIsInterface(p, Getattr(p, "type"))) {
return false;
}
return true;
}
/* ----------------------------------------------------------------------
* gcFunctionWrapper()
*