Bug 2421 – Struct assignment is broken (nulls target before evaluating source)

When you assign a struct value to a struct variable, the variable is under some circumstances nulled before evaluating the value. This leads to miscompilation if fields of the value depend on those of the variable. Test case: ----- module test; // Some lib-independence version(Tango) { import tango.io.Stdout; void show(Foo f) { Stdout.formatln("{} : {}", f.p, f.flag); } } else { import std.stdio; void show(Foo f) { writefln("%s : %s", f.p, f.flag); } } struct Foo { void* p; bool flag; } void main() { // Random non-zero values auto f = Foo(&show, true); // Prints correct non-zero values show(f); // Set to fresh copy of itself... f = Foo(f.p, f.flag); // prints {null} : false show(f); } ----- This seems to be as minimal as I can make it. Removing either field makes the problem go away, as does replacing the pointer with an int or float (but replacing the pointer with an object reference or double doesn't). $ gdc --version gdc (GCC) 4.1.3 20070831 (prerelease gdc 0.25, using dmd 1.021) (Ubuntu 0.25-4.1.2-16ubuntu1)

I cannot reproduce this on gdc 0.25 using dmd 1.060 with gcc-4.1.2 and gcc-4.3.5.