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Add QIntC::range_check_subtract

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This commit is contained in:
Jay Berkenbilt 2021-11-04 13:52:41 -04:00
parent 4a648b9a00
commit ec09b91443
4 changed files with 73 additions and 0 deletions
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4
ChangeLog
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@ -1,5 +1,9 @@
2021-11-04 Jay Berkenbilt <ejb@ql.org>
* Add QIntC::range_check_substract to do range checking on
subtraction, which has different boundary conditions from
addition.
* Bug fix: fix crash that could occur under certain conditions
when using --pages with files that had form fields. Fixes #548.

28
include/qpdf/QIntC.hh
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@ -250,6 +250,34 @@ namespace QIntC // QIntC = qpdf Integer Conversion
throw std::range_error(msg.str());
}
}
template <typename T>
void range_check_substract(T const& cur, T const& delta)
{
if ((delta >= 0) == (cur >= 0))
{
return;
}
if ((delta > 0) &&
((std::numeric_limits<T>::min() + delta) > cur))
{
std::ostringstream msg;
msg.imbue(std::locale::classic());
msg << "subtracting " << delta << " from " << cur
<< " would cause an integer underflow";
throw std::range_error(msg.str());
}
else if ((delta < 0) &&
((std::numeric_limits<T>::max() + delta) < cur))
{
std::ostringstream msg;
msg.imbue(std::locale::classic());
msg << "subtracting " << delta << " from " << cur
<< " would cause an integer overflow";
throw std::range_error(msg.str());
}
}
};
#endif // QINTC_HH

32
libtests/qintc.cc
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@ -48,6 +48,29 @@ static void try_range_check_real(
std::cout << ((passed == exp_pass) ? " PASSED" : " FAILED") << std::endl;
}
#define try_range_check_subtract(exp_pass, a, b) \
try_range_check_subtract_real(#a " - " #b, exp_pass, a, b)
template <typename T>
static void try_range_check_subtract_real(
char const* description, bool exp_pass,
T const& a, T const& b)
{
bool passed = false;
try
{
QIntC::range_check_substract(a, b);
std::cout << description << ": okay";
passed = true;
}
catch (std::range_error& e)
{
std::cout << description << ": " << e.what();
passed = false;
}
std::cout << ((passed == exp_pass) ? " PASSED" : " FAILED") << std::endl;
}
int main()
{
uint32_t u1 = 3141592653U; // Too big for signed type
@ -96,5 +119,14 @@ int main()
try_range_check(false, min_ll, -1LL);
try_range_check(false, max_sc, max_sc);
try_range_check(true, '!', '#');
try_range_check_subtract(true, 1, 2);
try_range_check_subtract(true, -1, -2);
try_range_check_subtract(true, 1, 10);
try_range_check_subtract(true, -1, -10);
try_range_check_subtract(false, 0LL, min_ll);
try_range_check_subtract(false, 1LL, min_ll);
try_range_check_subtract(true, 0LL, max_ll);
try_range_check_subtract(true, -1LL, max_ll);
try_range_check_subtract(false, -2LL, max_ll);
return 0;
}

9
libtests/qtest/qintc/qintc.out
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@ -26,3 +26,12 @@ min_ll + 0LL: okay PASSED
min_ll + -1LL: adding -1 to -9223372036854775808 would cause an integer underflow PASSED
max_sc + max_sc: adding  to  would cause an integer overflow PASSED
'!' + '#': okay PASSED
1 - 2: okay PASSED
-1 - -2: okay PASSED
1 - 10: okay PASSED
-1 - -10: okay PASSED
0LL - min_ll: subtracting -9223372036854775808 from 0 would cause an integer overflow PASSED
1LL - min_ll: subtracting -9223372036854775808 from 1 would cause an integer overflow PASSED
0LL - max_ll: okay PASSED
-1LL - max_ll: okay PASSED
-2LL - max_ll: subtracting 9223372036854775807 from -2 would cause an integer underflow PASSED