Bug 5996 – ICE(expression.c) CTFE of erroneous auto return function

This is wrong D2 code, because min() is not defined: auto foo(int n) { uint two = 2, three = 3, five = 5; auto h = new typeof(two)[n]; h[0] = 1; auto x2 = two, x3 = three, x5 = five; int i, j, k; for (int w = 1; w < n; w++) { auto el = h[w] = min(x2, x3, x5); if (x2 == el) x2 = two * h[++i]; if (x3 == el) x3 = three * h[++j]; if (x5 == el) x5 = five * h[++k]; } return h[$ - 1]; } enum uint h = foo(1691); static assert(h == 2123366400); void main() {} DMD 2.053beta prints: Assertion failure: '0' on line 1601 in file 'expression.c' --------------------- If I have remove the three if() lines: auto foo(int n) { uint two = 2, three = 3, five = 5; auto h = new typeof(two)[n]; h[0] = 1; auto x2 = two, x3 = three, x5 = five; int i, j, k; for (int w = 1; w < n; w++) { auto el = h[w] = min(x2, x3, x5); } return h[$ - 1]; } enum uint h = foo(1691); static assert(h == 2123366400); void main() {} Now the error messages are: Error: array index 4294967295 is out of bounds [][0 .. 0] test2.d(10): Error: h[__dollar - 1u] cannot be interpreted at compile time test2.d(12): Error: cannot evaluate foo(1691) at compile time test2.d(12): Error: cannot evaluate foo(1691) at compile time test2.d(13): Error: static assert (foo(1691) == 2123366400u) is not evaluatable at compile time Note an error message without line number too. DMD 2.052 instead prints: test2.d(4): Error: array index 0 is out of bounds [][0..0] test2.d(12): Error: cannot evaluate foo(1691) at compile time test2.d(12): Error: cannot evaluate foo(1691) at compile time test2.d(12): Error: cannot evaluate foo(1691) at compile time test2.d(13): Error: static assert (foo(1691) == 2123366400u) is not evaluatable at compile time --------------------- If I remove "auto" as return type and put a "uint": uint foo(int n) { uint two = 2, three = 3, five = 5; auto h = new typeof(two)[n]; h[0] = 1; auto x2 = two, x3 = three, x5 = five; int i, j, k; for (int w = 1; w < n; w++) { auto el = h[w] = min(x2, x3, x5); } return h[$ - 1]; } enum uint h = foo(1691); static assert(h == 2123366400); void main() {} Finally the error messages are correct: test3.d(8): Error: undefined identifier min, did you mean function main? test3.d(12): Error: cannot evaluate foo(1691) at compile time -------------------------- Now adding the missing min() fixes the problem, and it works with auto return type too: T min(T)(T a, T b, T c) { return (a > b) ? ((b > c) ? c : b) : ((a > c) ? c : a); } auto foo(int n) { uint two = 2, three = 3, five = 5; auto h = new typeof(two)[n]; h[0] = 1; auto x2 = two, x3 = three, x5 = five; int i, j, k; for (int w = 1; w < n; w++) { auto el = h[w] = min(x2, x3, x5); if (x2 == el) x2 = two * h[++i]; if (x3 == el) x3 = three * h[++j]; if (x5 == el) x5 = five * h[++k]; } return h[$ - 1]; } enum uint h = foo(1691); static assert(h == 2125764000); void main() {}

Reduced test case: --------- auto bug5996() { if (anyOldGarbage) {} return 2; } enum uint h5996 = bug5996(); static assert(h5996 == 2);

(In reply to comment #1) > Reduced test case: My second example shows an error message with missing line number: Error: array index 4294967295 is out of bounds [][0 .. 0] I have reduced it to this, I think it's better to fix this before fixing your reduced test case: auto foo(int n) { auto h = new typeof(something)[n]; return h[$]; } enum uint f = foo(1); void main() {}

(In reply to comment #2) > (In reply to comment #1) > > Reduced test case: > > My second example shows an error message with missing line number: > Error: array index 4294967295 is out of bounds [][0 .. 0] > > I have reduced it to this, I think it's better to fix this before fixing your > reduced test case: > > auto foo(int n) { > auto h = new typeof(something)[n]; > return h[$]; > } > enum uint f = foo(1); > void main() {} It's a problem with the gagging system. It actually shouldn't get as far as CTFE, so the out-of-bounds error shouldn't happen.

Commit pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/baaa223916953667ef63c03448201bd1d18bcf48 Fix issue 5996 ICE(expression.c) CTFE of erroneous auto return function When running semantic3 on a function to determine its return value, errors must not be gagged. There is no chance to re-run semantic3 on it.