Bug 22218 – Dynamic casts across binary boundaries can easily fail

If there are TypeInfo duplicates in multiple binaries of a process, e.g., from templates instantiated in multiple binaries, dynamic casts can fail. E.g., the following code fails with LDC (v1.27) and GDC (v10.3) on Linux, somehow works with DMD on Linux though, and fails on Windows in general: ``` class C() {} version (DLL) { version (Windows) { import core.sys.windows.dll; mixin SimpleDllMain; } pragma(mangle, "foo") export Object foo(Object o) { assert(cast(C!()) o); // <-- fails here return new C!(); } } else { T getFunc(T)(const(char)* sym, string thisExePath) { import core.runtime : Runtime; version (Windows) { import core.sys.windows.winbase : GetProcAddress; return cast(T) Runtime.loadLibrary("dynamiccast.dll") .GetProcAddress(sym); } else version (Posix) { import core.sys.posix.dlfcn : dlsym; import core.stdc.string : strrchr; auto name = thisExePath ~ '\0'; const pathlen = strrchr(name.ptr, '/') - name.ptr + 1; name = name[0 .. pathlen] ~ "dynamiccast.so"; return cast(T) Runtime.loadLibrary(name) .dlsym(sym); } else static assert(0); } void main(string[] args) { auto c = new C!(); auto o = getFunc!(Object function(Object))("foo", args[0])(c); assert(cast(C!()) o); } } ``` To be built and run like this: $ dmd -shared dynamiccast.d -version=DLL -ofdynamiccast.so -fPIC -defaultlib=libphobos2.so $ dmd dynamiccast.d -ofdynamiccast -fPIC -defaultlib=libphobos2.so $ ./dynamiccast Related: https://issues.dlang.org/show_bug.cgi?id=7020

@kinke updated dlang/druntime pull request #3543 "Fix Issue 22218 - Dynamic casts across binary boundaries can easily fail" fixing this issue: - Fix Issue 22218 Actually fixed by the previous commits, just fixing up the rt.cast_ compile errors after the rebase. https://github.com/dlang/druntime/pull/3543

dlang/druntime pull request #3543 "Fix Issue 22218 - Dynamic casts across binary boundaries can easily fail" was merged into master: - 861ab5bb4f5de95499909afb9fb7123c2bb94b91 by Martin Kinkelin: Fix Issue 22218 Actually fixed by the previous commits, just fixing up the rt.cast_ compile errors after the rebase. https://github.com/dlang/druntime/pull/3543