On Fri, Mar 13, 2020 at 08:22:53PM +0000, wjoe via Digitalmars-d-learn wrote: [...] > So from what I understand, because, at least on Posix, since there's > only a symbol name there's nothing I can do in my loader to verify > that a function is or does what it claim to be/do. [...]
As far as I know, it's the same thing on Windows PE format. Basically, once your code is compiled down to the object file level, there really isn't anything at the level of higher programming language concepts anymore, like type signatures and stuff. As far as object files are concerned, it's just a bunch of opaque binary data with string labels tacked on them, plus some extra information like relocation data and other such OS-level concepts. What's in that opaque binary data isn't really the purview of the object file format; things like types and function signatures are an interpretation laid upon the data by higher-level application code. The OS doesn't know what it is, and doesn't care (nor should it, that's not its job). So given some arbitrary object file, there's really no real guarantee as to what the contents are inside. Anybody can craft an object file that exports symbol names that look like the symbols generated by some higher-level programming language, but the actual binary data the names point to may do something completely different. In fact, this is exactly why pragma(mangle) is so useful: Adam Ruppe's jni.d, for example, makes extensive use of this in order to make the D code inside the object file appear like Java JNI symbols to the JVM. D's C++ interop is also based on the same concept: export symbols that look like C++ mangled symbols, but inside is actually D code, not C++ code. Far from being "disappointing", I think this stuff is very powerful, and lots of fun if you do it right. But it does come with the caveat that you're essentially meddling around under the hood, so it's your responsibility not to do something that will cause the engine to blow up. Hence the @trusted tag. T -- Never step over a puddle, always step around it. Chances are that whatever made it is still dripping.