http://www.mail-archive.com/qemu-devel@nongnu.org/msg128802....
Your link above shows an author who claims JSON output, yet the output is clearly non-validating JSON (toplevel is not a [] or {}, improper quoting, etc). It appears that instead of using JSON serialization, the author merely printed key/value pairs separated by the string ": ". The problems with this approach are obvious.
This is why using a proper serialization format is important.
If the author had done this correctly and used a proper JSON library to produce this output, the following, completely safe result would have occurred:
{ "cluster_size":65536, "disk size":"136K", "file format":"qcow2", "image":"/tmp/foo\ncluster_size: bar", "virtual size":"10M (10485760 bytes)" }
The author probably would have been best served by YAML, which is more easily readable -- and which, like json, provides mechanisms to properly represent arbitrary data.
In any event, the discussion is severely confused. Ad-hoc buggy formats cannot be compared with well-formed JSON or YAML. This has nothing at all to do with the language.
It is a programming error, not an inherent flaw in the language.
In other words, those files aren't causing the QEMU program internals to re-interpolate one variable as two values. They're merely messing up a poorly written data exchange format.
Other languages such as I listed above simply do not have the same issue. The C program did not mis-interpret a variable as two separate values because it contained spaces. That is the nature of the danger with shell -- any reference to a variable in Bourne involves string interpolation and tokenization. This simply does not happen in C.