reading settings option list (getSettingInfo) fails using C if no option names set

[ahopper]

if the settings optionNames is not populated this

SoapySDR/lib/TypeHelpers.hpp

Line 140 in f8c1783

out.optionNames = toStrArray(info.optionNames, &out.numOptions);

resets the numOptions to 0 so the C api cannot see the options.

the lime driver has an example of not setting optionNames

https://github.com/myriadrf/LimeSuite/blob/e829d3ede6222c1c0fc0e90dcd2050e50569e33d/SoapyLMS7/Settings.cpp#L802-L807

[zuckschwerdt]

Just swappig the toStrArray() call order for out.options and out.optionNames should work right?
With options last it will take precedence over the result from optionNames -- a comment to the intention is then also needed ;)
Do you want to PR this change?

[ahopper]

Yep that should work, I'm happy to create a PR.

[ericek111]

Now, if the option names are not supplied (as they are optional), the optionNames list is not properly initialized, causing a crash upon reading the junk char*s. :D

Honestly, I'd just shove size_t numOptionNames into the SoapySDRArgInfo struct, but that would break ABI. Another option is to pre-fill the names with NULLs (sizeof(char*) * out.numOptions, as returned for the options list):

-static inline char **toStrArray(const std::vector<std::string> &strs, size_t *length)
-{
-    auto out = callocArrayType<char *>(strs.size());
+static inline char **toStrArray(const std::vector<std::string> &strs, size_t *length, size_t minLength = 0)
+{
+    auto out = callocArrayType<char *>(std::max(minLength, strs.size()));

What do you think?

[zuckschwerdt]

Good point and a nice fix indeed. PR if you like.
Please include e.g. …size of the options and optionNames set, …
at https://github.com/pothosware/SoapySDR/blob/master/include/SoapySDR/Types.h#L94
and When null or emtpy, the option value…
at https://github.com/pothosware/SoapySDR/blob/master/include/SoapySDR/Types.h#L105

[guruofquality]

Another way would be to copy options into optionNames when the info.optionNames is empty. Any app looking for a displayable name for the option would just use the option string itself if optionNames was empty.