RFR: 8227493: Return a more useful error message from lookupAllHostAddr if getaddrinfo results in EAI_SYSTEM error [v2]

[Jaikiran Pai]

On Mon, 2 Dec 2024 15:32:34 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> src/java.base/unix/native/libnet/net_util_md.c line 190:
>> 
>>> 188:         sys_errno_string = strerror(sys_errno);
>>> 189:         format = "%s: %s: %s";
>>> 190:         size = strlen(format) + strlen(hostname) + strlen(error_string) + strlen(sys_errno_string) + 2;
>> 
>> should be + 4, not + 2 here
>
> Actually, IIANM, shouldn't it be + 5 here and + 3 below to account for the null terminator?
> snprintf says it will write up to size - 1 characters.

You are right about + 3 instead of + 2. Furthermore, now that you mention it, I'm not sure why there's a `strlen(format)` in that size computation. The original change was introduced in https://hg.openjdk.org/jdk7/jdk7/jdk/rev/b5d37597c815 and at that time it was using `sprintf` (and not `snprintf`) and the `sprintf` as per its documentation, considers size to be `INT_MAX + 1`, so `size` wasn't being passed to it and only used for `malloc()`. Even then, I don't understand why `strlen(format)` (or even + 2) was considered for the size.

I have updated this part of the PR, but I'm going to look at this size computation bit more tomorrow with a fresh mind.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22484#discussion_r1866170010