Mavgen WLUA: Fix incorrect display of negative ints on mac #944
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Fix is to not include the value argument when calling add_le function, and let Wireshark do the value extraction internally. This avoids an issue where a double being cast to a unsigned int (which should have been an int), becomes 0 on mac, but works on Linux. The value argument is still required in the case when a float is used to represent an enum or bitmask. Also, value is used seperately when adding unit conversions and when doing any bitmask extraction
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lgtm! |
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This PR is to fix mavlink/mavlink#1862, fix mavlink/mavlink#2073 and fix #701. (In particular mavlink/mavlink#2073 includes the discussion about how it was figured out!).
There is a bug in wireshark, whereby a double is cast to an unsigned int when it should be a signed int, before being used as a signed int. On Linux this works, but on Mac negative values get cut to zero (here is why).
Thanks to @rotu, a Wireshark fix has been merged in wireshark/wireshark#15438.
This PR provides a workaround/fix to avoid the issue completely, so that it will work even with older versions of Wireshark.
The fix is to not include the value argument when calling add_le function, and let Wireshark do the value extraction internally from the raw bytes. This avoids the code which does the bad casting. It also makes the generated lua file have about 20-25% fewer lines of code.
There are some case in which the value still needs to separately extracted:
I've tested new LUA with some basic scenarios on Linux, and the CI also includes a decent selection of pytests for this.
@rotu