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Fix overflow in tm formatter #2564

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merged 1 commit into from
Oct 27, 2021
Merged

Fix overflow in tm formatter #2564

merged 1 commit into from
Oct 27, 2021

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phprus
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@phprus phprus commented Oct 24, 2021

Fix possible overflow errors in tm formatter on invalid tm values.

@phprus phprus mentioned this pull request Oct 24, 2021
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@phprus phprus force-pushed the optimize-tm-formatting-3-ub-2 branch 3 times, most recently from 0a1a08e to 0465eca Compare October 25, 2021 15:10
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phprus commented Oct 26, 2021

@vitaut, review this PR please.
This is fixing year overflow and possible overflow on all digits2 calls (is tm is invalid).

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vitaut reviewed Oct 27, 2021
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Thanks for the fix. Looks good overall, just a few minor comments inline.

include/fmt/chrono.h Outdated
@@ -1406,80 +1406,112 @@ template <typename OutputIt, typename Char> class tm_writer {
OutputIt out_;
const std::tm& tm_;

auto tm_year() const noexcept -> int { return 1900 + tm_.tm_year; }
auto tm_sec() const noexcept -> int {
FMT_ASSERT(tm_.tm_sec >= 0 && tm_.tm_sec <= 60, "");
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According to https://pubs.opengroup.org/onlinepubs/7908799/xsh/time.h.html tm_sec should be in the range [0, 61] so the upper bound should be 61 here.

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It's [0..60] since C99 and C++11.
https://en.cppreference.com/w/c/chrono/tm
https://en.cppreference.com/w/cpp/chrono/c/tm

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For compatibility, I changed the interval to [0, 61].

include/fmt/chrono.h Outdated Show resolved Hide resolved
include/fmt/chrono.h
return tm_.tm_yday;
}

auto tm_hour12() const noexcept -> int {
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I suggest merging this function into on_12_hour since it's not used anywhere else.

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The function tm_hour12 will be used in on_12_hour_time. PR #2550 (https://github.com/fmtlib/fmt/pull/2550/files#diff-5d08eff445a9a7793fbd22d873b2284f0ae69f1550aff06f673de49768bccca0R1744-R1750)

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OK, let's keep it then.

include/fmt/chrono.h Show resolved Hide resolved
@phprus
Add FMT_ASSERT and validation of values of struct tm members
75f7dd2 
Switch internal year calculations to long long
@phprus phprus force-pushed the optimize-tm-formatting-3-ub-2 branch from 0465eca to 75f7dd2 Compare October 27, 2021 20:14
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phprus commented Oct 27, 2021

@vitaut
Something broke on documentation build...
https://github.com/fmtlib/fmt/runs/4027135638?check_suite_focus=true

Exception occurred:
  File "/home/runner/work/fmt/build/virtualenv/lib/python3.8/site-packages/docutils/writers/html5_polyglot/__init__.py", line 445, in section_title_tags
    if (ids and self.settings.section_self_link
AttributeError: 'Values' object has no attribute 'section_self_link'

@vitaut vitaut merged commit 90034e4 into fmtlib:master Oct 27, 2021
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vitaut commented Oct 27, 2021

The documentation issue looks unrelated, merged.

PoetaKodu pushed a commit to pacc-repo/fmt that referenced this pull request Nov 11, 2021
@phprus @PoetaKodu
Add FMT_ASSERT and validation of values of struct tm members (fmtlib#…
314e4e6 
…2564)

Switch internal year calculations to long long
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