DMD Linker Prob

A linker problem I encountered earlier and resolved with the help of Adam Ruppe ( @destructionator ).

TL;DR

Run your linker error through ddemangle

You'll get something that looks like ...

bool dchip.cpBody.cpBody.__xopEquals(ref const(dchip.cpBody.cpBody), ref const(dchip.cpBody.cpBody))

In your code, pull in the typeid of the offending data structure.

auto x = typeid(cpBody).toString();

Steps To Reproduce

• Clone DChip from here
• Add dchip to your dub repository dub add-local <path_to_dchip>
• Run dub in this repo to verify linker problem

dub

or

dub --config=doomedToFailure

• Verify the workaround (should succeed this time)

dub --config=workaround

What's going on?

Good question :-) It looks like copying a pointer to a cpBody struct in the line.

bods ~= bod;

is causing DMD to insert a reference to the cpBody structs TypeInfo which fails to link.

Linking... .dub/build/doomedToFailure-debug-linux.posix-x86_64-dmd_2068-526FACB894EDABA2E3C35CF8E3068673/dmdlinkerprob.o:(.data._D30TypeInfo_S5dchip6cpBody6cpBody6__initZ+0x38): undefined reference to _D5dchip6cpBody6cpBody11__xopEqualsFKxS5dchip6cpBody6cpBodyKxS5dchip6cpBody6cpBodyZb collect2: error: ld returned 1 exit status

(If you're curious comment out the bods ~= bod; line. The project will compile - verifying this one to be the problematic line.)

Running ddemangle on the linker error shows that the bad function is.

bool dchip.cpBody.cpBody.__xopEquals(ref const(dchip.cpBody.cpBody), ref const(dchip.cpBody.cpBody))

How do we fix it??

Adam's workaround is to force DMD to pull in the the cpBody's TypeInfo explicitly ...

auto x = typeid(cpBody).toString();

Running dub with --config=workaround enables a version block which includes Adams workaround.

So now the code compiles. All is well!