I get this assertion when running reftests in a local beta debug build on Linux64. Looking at the blame I guess it's a regression from bug 1227023. The call comes from here: http://hg.mozilla.org/mozilla-central/annotate/ad1f85f172b7/xpcom/base/nsSystemInfo.cpp#l706

This makes the assertion go away, fwiw.

Comment on attachment 8707680 [details] [diff] [review] fix? Thank you. That is what I was thinking the length argument was for.

And that's actually what I was meaning to do, but failed to.

Looking through the uses of IsTerminated(), I think this will only cause real problems if secondaryLibrary is used together with nsPromiseFlatCString. secondaryLibrary is only read from javascript and concatenated among other strings. I don't know what code does js reads, but I think use of nsPromiseFlatCString would be unlikely. I ran valgrind --tool=memcheck on amd64 firefox-44.0b8, checked for updates, and no uninitialized reads were reported.

Comment on attachment 8707680 [details] [diff] [review] fix? Approval Request Comment [Feature/regressing bug #]: bug 1227023 [User impact if declined]: I don't expect any problems from this bug on its own, but the patch is required for the patch in bug 1245745 to apply cleanly to 45. [Describe test coverage new/current, TreeHerder]: There are existing tests running this code, but they don't expect any particular string AFAIK. [Risks and why]: low [String/UUID change made/needed]: none

Comment on attachment 8707680 [details] [diff] [review] fix? Necessary for bug 1245745

For your reference I also hit this with vanilla firefox-44.0: ASSERTION: nsTDependentString must wrap only null-terminated strings. You are probably looking for nsTDependentSubstring.: 'mData[mLength] == 0', file ../../dist/include/nsTString.h, line 455