#define ANNOTATE(property) __attribute__((tag(property))) struct Cell { int f; } ANNOTATE("GC Thing"); class AutoSuppressGC_Base { public: AutoSuppressGC_Base() {} ~AutoSuppressGC_Base() {} } ANNOTATE("Suppress GC"); class AutoSuppressGC_Child : public AutoSuppressGC_Base { public: AutoSuppressGC_Child() : AutoSuppressGC_Base() {} }; class AutoSuppressGC { AutoSuppressGC_Child helpImBeingSuppressed; public: AutoSuppressGC() {} }; extern void GC() ANNOTATE("GC Call"); void GC() { // If the implementation is too trivial, the function body won't be emitted at all. asm(""); } extern void foo(Cell*); void suppressedFunction() { GC(); // Calls GC, but is always called within AutoSuppressGC } void halfSuppressedFunction() { GC(); // Calls GC, but is sometimes called within AutoSuppressGC } void unsuppressedFunction() { GC(); // Calls GC, never within AutoSuppressGC } void f() { Cell* cell1 = nullptr; Cell* cell2 = nullptr; Cell* cell3 = nullptr; { AutoSuppressGC nogc; suppressedFunction(); halfSuppressedFunction(); } foo(cell1); halfSuppressedFunction(); foo(cell2); unsuppressedFunction(); { // Old bug: it would look from the first AutoSuppressGC constructor it // found to the last destructor. This statement *should* have no effect. AutoSuppressGC nogc; } foo(cell3); }