clyne/constexpr-to-string
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Fixed potential bug with -MINIMUM_VALUE

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Original code had something like `N < 0 ? -N : N` which could fail if `N` has minimum value of appropriate type. For example, in original code this could fail:
```cpp
const long long int LL_MIN = std::numeric_limits<long long int>::min(); //probably: -9223372036854775808
static const char *number = to_string<LL_MIN, 10>;
```

Also note that this code relies on "modulo on negative first operands" which was implementation defined in C++03 and before, but with C++11 and later it is defined by standard (see `ISO14882:2011(e)`), and this code anyway targets C++17 so we're safe here.
This commit is contained in:
EnilPajic 2020-06-26 21:25:39 +02:00 committed by GitHub
parent 2be778931d
commit 5baf5d3dae
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1 changed files with 3 additions and 3 deletions
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6
to_string.hpp
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@ -23,7 +23,7 @@ struct to_string_t {
// fits to the number perfectly.
char buf[([] {
unsigned int len = N >= 0 ? 1 : 2;
for (auto n = N < 0 ? -N : N; n; len++, n /= base);
for (auto n = N; n; len++, n /= base);
return len;
}())];
@ -33,8 +33,8 @@ struct to_string_t {
constexpr to_string_t() {
auto ptr = buf + sizeof(buf) / sizeof(buf[0]);
*--ptr = '\0';
for (auto n = N < 0 ? -N : N; n; n /= base)
*--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[n % base];
for (auto n = N; n; n /= base)
*--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[(N < 0 ? -1 : 1) * (n % base)];
if (N < 0)
*--ptr = '-';
}