Recently, our big project began crashing on unhandled division by zero. No recent code seems to contain any likely elements so it may be new data sets affecting old code. The problem is the code base is pretty big, and running on an embedded device with no comfortable debug access (debug is done by a lot of printf()s over serial console, there is no gdb for the device and even if there was, the binary compiled with debug symbols wouldn’t fit).
The most viable way would likely be to find all the division operations (they are relatively infrequent), and analyze code surrounding each of them to see if any of the divisor variables was left unguarded.
The question is then either how to find all division operations in a big (~200 files, some big) C++ project, or, if you have a better idea how to locate the error, please give them.
extra info: project runs on embedded ARM9, a small custom Linux distro, crosscompiled with Cygwin/Windows crosstools, IDE is Eclipse but there’s also Cygwin with all the respective goodies. Thing is the project is very hardware-specific, and the crashes occur only when running at full capacity, all the essential interconnected modules active. Restricted “fault mode” where only bare bones are active doesn’t create them.
Finding all of the divisions shouldn’t be hard with a custom grep search. You can easily distinguish that usage from other usages of the
/and%character in C++.Also, if you know what you are dividing, you could globally overload the
/and%operator to have a__FILE__and__LINE__informing assertion. If using a makefile, it shouldn’t be hard to include the custom operator code in all the linked files without touching the code.