Bug 4004 – DMD 2.042 CTFE regression with functions taking ref parameters

There appears to be a weird regression introduced in DMD 2.042 with the compile time handling of ref parameters (runtime versions of the function are unaffected). It appears that when a function taking a ref parameter passes it as a ref parameter to another function. If the first function modifies the parameter then modifications made by the second function won't be observed. Below is a very simple test case: import std.stdio: writeln; void foo2(ref size_t offset) { offset = 8; } void foo(ref size_t offset) { auto okay = offset; // Reading from the ref param is okay offset += 0; // comment this line out and it works foo2(offset); } size_t bar() { size_t offset = 0; foo(offset); return offset; } template foobar() { immutable foobar = bar; } void main(string[] args) { writeln(foobar!(),'\t', bar ); // prints 0 8 instead of 8 8 }

Reduced test case for test suite. -------- void bug4004a(ref int a) { assert(a==7); a+=3; } void bug4004b(ref int b) { b= 7; bug4004a(b); } int bug4004c() { int offset = 5; bug4004b(offset); return offset; } static assert(bug4004c()==10); ------------------------- PATCH: Index: interpret.c =================================================================== --- interpret.c (revision 420) +++ interpret.c (working copy) @@ -53,7 +53,7 @@ Expression *interpret_values(InterState *istate, Expression *earg, FuncDeclaration *fd); ArrayLiteralExp *createBlockDuplicatedArrayLiteral(Type *type, Expression *elem, size_t dim); -Expression * resolveReferences(Expression *e, Expression *thisval); +Expression * resolveReferences(Expression *e, Expression *thisval, bool *isReference = NULL); /************************************* * Attempt to interpret a function given the arguments. @@ -1107,8 +1107,11 @@ // ------------------------------------------------------------- // The variable used in a dotvar, index, or slice expression, // after 'out', 'ref', and 'this' have been removed. -Expression * resolveReferences(Expression *e, Expression *thisval) +// *isReference will be set to true if a reference was removed. +Expression * resolveReferences(Expression *e, Expression *thisval, bool *isReference /*=NULL */) { + if (isReference) + *isReference = false; for(;;) { if (e->op == TOKthis) @@ -1131,6 +1134,8 @@ VarExp *ve2 = (VarExp *)v->value; if (!ve2->var->isSymbolDeclaration()) { + if (isReference) + *isReference = true; e = v->value; continue; } @@ -2087,7 +2092,8 @@ v->value = e2; return e2; } - e1 = resolveReferences(e1, istate->localThis); + bool destinationIsReference = false; + e1 = resolveReferences(e1, istate->localThis, &destinationIsReference); // Unless we have a simple var assignment, we're // only modifying part of the variable. @@ -2167,7 +2174,8 @@ { VarExp *ve = (VarExp *)e1; VarDeclaration *v = ve->var->isVarDeclaration(); - addVarToInterstate(istate, v); + if (!destinationIsReference) + addVarToInterstate(istate, v); v->value = newval; } else if (e1->op == TOKindex)

changeset 429