Fix segfault if a file from an invalid searchpath-entry is attempted to get built #3764
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…to get built When I try to build an expression from a searchpath that happens to be wrong, `nix-build` segfaults: ``` λ ma27 [~] → nix-build '<foo/bar>' -I foo=$(mktemp -d) [1] 16252 segmentation fault (core dumped) nix-build '<foo/bar>' -I foo=$(mktemp -d) ``` This happens if the `file`-Symbol in the `Pos` struct doesn't have a value (due to the missing searchpath-entry). This causes a segfault when the `Error`-implementation tries to cast `Pos` to an `ErrPos`. This was most likely caused by 55eb717, previously it was explicitly checked if `pos` has any value. This patch basically switches back to this behavior by setting `nixCode` to `std::nullopt` if `pos` is incomplete. Also added a testcase to make sure that this doesn't appear again in the future.
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cc @edolstra @domenkozar @bburdette |
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Good find. I came across something similar in my show-trace branch, in a different context. I've got a PR out for the general case of pos->errpos conversion, here: #3767 |
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Is this PR still necessary after #3767? |
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Appears to work now. |
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When I try to build an expression from a searchpath that happens to be
wrong,
nix-buildsegfaults:This happens if the
file-Symbol in thePosstruct doesn't have avalue (due to the missing searchpath-entry). This causes a segfault
when the
Error-implementation tries to castPosto anErrPos.This was most likely caused by 55eb717,
previously it was explicitly checked if
poshas any value. This patchbasically switches back to this behavior by setting
nixCodetostd::nulloptifposis incomplete.Also added a testcase to make sure that this doesn't appear again in the
future.