Possible bug in binutils for MinGW-w64 related to linking weak symbols

[Martin Storsjö]

On Thu, 19 Mar 2026, Martin Storsjö wrote:

> When you use a declaration of a weak symbol (which means that the symbol 
> either may be defined, or may be undefined, when it essentially is a null 
> pointer), then the symbol "bar" points at an absolute symbol with the address 
> zero. The idea here is that if nothing else overrides the symbol, then it 
> uses the fallback value of absolute zero (and in that case, the user should 
> check if it is null before referencing it).

Sorry, I misremembered one detail here. The default symbol it points at 
isn't an absolute zero symbol, it's an undefined symbol. That makes it 
easier to disambiguate between a weak external pointing at an actual 
definition (which should be preferred), and a weak external pointing at an 
undefined symbol (which is just a dummy).


FWIW, from when I implemented this in LLVM, I made a set of unit tests for 
linking of weak symbols - see https://martin.st/temp/weak-testcases.zip.

// Martin