Auto merge of #39095 - nagisa:fix-ub-in-testhelp, r=alexcrichton
Auto merge of #39095 - nagisa:fix-ub-in-testhelp, r=alexcrichton

Fix UB in test helpers

Macro expansion producing defined has undefined behavior in C/C++.

aidancully/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust