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e36659c82f
Problem:
Various out-of-bounds writes inherited from vim (examples assume MAXPATHL==4096):
- truncated item groups where minwid>maxwid:
nvim --clean +"set stl=%<%{%repeat('x',4096-11)%}%50.5(12🙂345%)"
leads to fillchars spilling over the end of the group/buffer while trying to
compensate for truncating at a multicell character because minwid<=maxwid is assumed
- left-aligned item groups with multi-byte fillchar:
nvim --clean +"set fillchars+=stl:∙ stl=%<%{%repeat('x',4096-3)%}%-2(X%)"
wrongly leads to padding at the end of the statusline and `out_p-out==4097`
because the bounds check assumes a 1-byte fillchar
- right-aligned item groups with 1-byte fillchar:
nvim --clean +"set stl=%<%{%repeat('x',4096-4)%}%4(XY%)"
leads to "YX" instead of "XY" at the end of the statusline
because `memmove` is done before adjusting the offset
- right-aligned item groups with multi-byte fillchar:
nvim --clean +"set fillchars+=stl:∙ stl=%5(X%)"
leads to "∙∙∙∙<e2>", i.e. the fillchar is being written over the group contents
and eventually being overwritten itself at the second byte with the final NUL,
because the padding counter assumes a 1-byte fillchar; to crash Neovim,
nvim --clean +"set fillchars+=stl:∙ stl=%<%{%repeat('x',4096-149)%}%50(X%)"
Solution:
Clearer variable names and no recycling of variables for different purposes.