This is a big forwards-compatibility risk. Suppose glibc adds a new symbol, and then a GPU driver adds a dependency on that symbol. The user wants to run an old executable with the updated GPU driver (maybe the old GPU driver doesn’t support their GPU). Normally, this would work fine: the user has to use a new copy of glibc, which will be compatible with both the new GPU driver and the old executable. But with your approach, the GPU driver is forced to use the glibc reimplementation which has been statically linked into the executable. Which, since the executable is old, can’t possibly implement the new symbol.
The same issue would occur if glibc adds a new version of an existing symbol and then the GPU driver is recompiled. (Or, for that matter, if a GPU driver adds a dependency on a symbol which glibc has always supported but which isn’t in the subset that you reimplemented, though in theory that could be solved if you reimplemented 100% of the symbols.)
The same issue would occur if glibc adds a new version of an existing symbol and then the GPU driver is recompiled. (Or, for that matter, if a GPU driver adds a dependency on a symbol which glibc has always supported but which isn’t in the subset that you reimplemented, though in theory that could be solved if you reimplemented 100% of the symbols.)