mirror of
https://github.com/nim-lang/Nim.git
synced 2025-12-29 17:34:43 +00:00
fe8b84496f
This is taken from:af69b3ceaeFull original comment: This is to avoid heavy inlining happening when two allocation calls would occur shortly after each other. This inlining would sometimes be accompanied with an optimisation as the compiler is able to see that cellToUsr ending the first allocation call is shortly followed by an usrToCell call. The pointer arithmetic is redundant and the compiler can eliminate it, leaving only the cell address in a register (and later the stack) instead of the actual pointer to the user data, as one would expect. This combined with a GC collect cycle will cause the stack scan to only notice the cell address, which is of no good due to a usrToCell in the gcMark call which shifts that address to an adjacent cell. This means that the actual cell of importance will not get marked and thus cause a premature collection of that cell. BOOM. (cherry picked from commit40093b4a93)