It defines how an application interacts with itself, how an application interacts with the kernel, and how an application interacts with libraries. The common explanation for not fixing some issues with c++ is that it would break the abi and require recompilation, but on the other hand i encounter statements like this An abi is a mapping from the execution model of the language to a particular machine/operating system/compiler combination It makes no sense to define one in the language specification because that runs the risk of excluding c implementations on some architectures. See also the x86 tag wiki for other guides / references / links This is a case where your matrix package is too old
The version number you give in the title is an rstudio version number, which isn't useful here If possible you should update the matrix package to 1.7.0 However, you can only do this if you're running r version 4.4 Otherwise, you should reinstall lme4 from source, or from a repository with a consistently built binary matrix / lme4 stack. This is used for calling c library (libc) functions on linux from assembly An abi standard for any language really needs to come from a given platform that wants to support such a thing
