[b2] std::length_error crash when empty string is passed to var_defines on LoongArch #786

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1. iv-m commented on Jul 1, 2026

   

   iv-m

   on Jul 1, 2026

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   I've just stumbled upon this on my loongarch64 machine. Trivial fix like this seems to help:

   --- a/boost/tools/build/src/engine/variable.cpp
   +++ b/boost/tools/build/src/engine/variable.cpp
   @@ -78,6 +78,7 @@ void var_defines(struct module_t * module, const char * const * e, int preproces
           for (; *e; ++e)
           {
                   ::b2::string_view def(*e);
   +               if (def.empty()) continue;
                   ::b2::string_view var(def.begin(), def.find('='));
                   ::b2::string_view val(def.begin() + var.size() + 1);
                   b2::jam::variable jam_var { module,

   But I'm not sure if this is the right thing to do, or why this empty string is passed here in the first place.
2. iv-m commented on Jul 1, 2026

   

   iv-m

   on Jul 1, 2026

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   BTW this issue probably should be moved to https://github.com/boostorg/build/issues.
3. iv-m commented on Aug 14, 2026

   

   iv-m

   on Aug 14, 2026

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   This might be fixed in 708353c

   👍React with 👍1Reacted by Weijia Wang
4. pdimov commented on Oct 28, 2026

   

   pdimov

   on Oct 28, 2026

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   I can move this issue to boostorg/build, but the upstream repository of B2 is https://github.com/bfgroup/b2, and I can't move it there. :-)
5. pdimov

   transferred this issue fromboostorg/booston Oct 28, 2026
6. grafikrobot commented on Oct 28, 2026

   

   grafikrobot

   on Oct 28, 2026

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   3. This might be fixed in 708353c

   Yes, certain that is the fix. And you can try it out by using a more recent b2 (which you can do with any Boost version).