halting problem :: Linking against JSON-GLib < 0.16 and Pulseaudio

:: ~2 min read

this is a public announcement.

if you link against PulseAudio, whether you want it or not, you’ll get an automatic dependency on json-c, a small C library that parses JSON and doesn’t have any dependency1. sadly, json-c leaks symbols all over the place, and one of them is called json_object_get_type()2.

JSON-GLib, the library that yours truly wrote about 6 years ago to parse JSON using a decent C library as a base, also has a type called json_object_get_type()3.

if you link against PulseAudio and JSON-GLib4 then you’ll get a segmentation fault with a weird stack trace, like this one and its duplicates5.

the solution is to depend on a version of JSON-GLib greater than 0.16.1, which builds JSON-GLib with the -Bsymbolic linker flag6.

that would be all.


  1. which is arguably a plus for a system dæmon 

  2. which returns an integer for I don’t know which reason 

  3. which returns a GType for the JsonObject boxed structure, so you can use them in properties and signal marshallers; as it happens, GType is a long look-alike 

  4. or any other library that depends on JSON-GLib, like Clutter 

  5. since both return values and arguments of the functions above are compatible, the linker won’t moan about it, so you won’t see any warning or error when building your code 

  6. another solution is to statically link json-c inside PulseAudio instead of dynamically linking it; another solution is to link json-c with -Bsymbolic; yet another solution would be for PA to not use a dependency to parse JSON – or drop JSON entirely because I can’t for the life of me understand why an audio server is dealing with JSON at all 

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