Is returning a value != '0' or '1' as jboolean from a JNI function legal? (original) (raw)
Jason Greene jason.greene at redhat.com
Mon Aug 20 19:25:32 UTC 2018
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On Aug 20, 2018, at 12:23 PM, Andrew Haley <aph at redhat.com> wrote:
On 08/20/2018 04:14 PM, Jason Greene wrote:
IMO departing from C semantics (non-zero = TRUE, zero = false) offers little gain and will likely just lead to hard to catch bugs. Even if the JNI developer knows the rules, it will be quite easy for surprises to show up. For example, a developer might assume a library call always returns 1, and wire it straight to a boolean. If this assumption is broken (a condition not taken into account, or future behavioral differences), then it could quickly turn into a lot of wasted time and effort. It's tricky, though: a C implementation could silently truncate a value of 0xff000000 to (jboolean) 0x00, and there's not a damn thing that a JVM can do about it: there's literally no way to know. It's pretty much unfixable from our end.
OK but in that case the C developer can see its an unsigned char, and their compiler is likely to throw an overflow warning. Granted, it’s also true that int is a more common return value than unsigned char.
-Jason
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