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test-cutils: Test more integer corner cases
We have quite a few undertested and underdocumented integer parsing corner cases. To ensure that any changes we make in the code are intentional rather than accidental semantic changes, it is time to add more unit tests of existing behavior. In particular, this demonstrates that parse_uint() and qemu_strtou64() behave differently. For "-0", it's hard to argue why parse_uint needs to reject it (it's not a negative integer), but the documentation sort of mentions it; but it is intentional that all other negative values are treated as ERANGE with value 0 (compared to qemu_strtou64() treating "-2" as success and UINT64_MAX-1, for example). Also, when mixing overflow/underflow with a check for no trailing junk, parse_uint_full favors ERANGE over EINVAL, while qemu_strto[iu]* favor EINVAL. This behavior is outside the C standard, so we can pick whatever we want, but it would be nice to be consistent. Note that C requires that "9223372036854775808" fail strtoll() with ERANGE/INT64_MAX, but "-9223372036854775808" pass with INT64_MIN; we weren't testing this. For strtol(), the behavior depends on whether long is 32- or 64-bits (the cutoff point either being the same as strtoll() or at "-2147483648"). Meanwhile, C is clear that "-18446744073709551615" pass stroull() (but not strtoll) with value 1, even though we want it to fail parse_uint(). And although qemu_strtoui() has no C counterpart, it makes more sense if we design it like 32-bit strtoul() (that is, where "-4294967296" be an alternate acceptable spelling for "1", but "-0xffffffff00000001" should be treated as overflow and return 0xffffffff rather than 1). We aren't there yet, so some of the tests added in this patch have FIXME comments. However, note that C2x will (likely) be adding a SILENT semantic change, where C17 strtol("0b1", &ep, 2) returns 0 with ep="b1", but C2x will have it return 1 with ep="". I did not feel like adding testing for those corner cases, in part because the next version of C is not standard and libc support for binary parsing is not yet wide-spread (as of this patch, glibc.git still misparses bare "0b": https://sourceware.org/bugzilla/show_bug.cgi?id=30371). Message-Id: <20230522190441.64278-5-eblake@redhat.com> [eblake: fix a few typos spotted by Hanna] Reviewed-by: Hanna Czenczek <hreitz@redhat.com> [eblake: fix typo on platforms with 32-bit long] Signed-off-by: Eric Blake <eblake@redhat.com>
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