Bug 3190 – enum doesn't work as the increment in a for loop

The following should print a list of numbers from 0 to 10: enum real ONE = 1.0; real x; for (x=0.0; x<10.0; x+=ONE) writeln(x); writeln(x); Instead it prints: 0 nan I.e. the loop is only executed once, and x is set to NaN after the first iteration. The same happens if float is used instead of real. If double is used, the program goes into a near-infinite loop, spitting out very small numbers (starting with 6.65345e-316). The following makes the program behave as expected: - making ONE a normal variable instead of an enum - writing "enum { real ONE }" instead - putting the increment inside the loop body

I suspect this is related to bug#2414 or bug#2998. There's definitely something badly wrong with D2 enum (manifest constant) assignment.

There are two problems here. PROBLEM 1: This problem only shows up in for() loops because the increment condition isn't doing constant folding. This is a more general problem, which also affects D1. statement.c line 1160 (DMD 2.032). if (increment) { increment = increment->semantic(sc); increment = resolveProperties(sc, increment); + increment = increment->optimize(0); } This change is enough to make the bug go away, but there's another oddity: PROBLEM 2: It only happens for enum real ONE = 1.0; but not for enum : real { ONE = 1.0 }. This is because expression.c DsymbolExp::semantic(Scope *sc) checks for enum members, but not for the new D2 manifest constants. I suspect that it probably should convert them, too, as in this second patch: expression.c, line 2168. if (v) { //printf("Identifier '%s' is a variable, type '%s'\n", toChars(), v->type->toChars()); if (!type) { type = v->type; if (!v->type) { error("forward reference of %s %s", v->kind(), v->toChars()); type = Type::terror; } } + if ((v->storage_class & STCmanifest) && v->init) { + e = v->init->toExpression(); + e->semantic(sc); + return e; + } e = new VarExp(loc, v); e->type = type; e = e->semantic(sc); return e->deref(); }

*** Issue 3394 has been marked as a duplicate of this issue. ***

Fixed DMD2.035.