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replace mod_inv_25 by explicit value as a fix for VS warning C4307 #3450

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merged 1 commit into from
May 18, 2023

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florimond-collette
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@florimond-collette florimond-collette commented May 17, 2023

revert non-working workaround for issue #3163

This fix for warning C4307: '*': integral constant overflow leads to warning C4309: 'static_cast': truncation of constant value, which is not better (both are level 3 VS warnings). Revert to the original code that is clearer and also present further in this source code.

Alternatively, to avoid any VS warning, one could follow the third suggestion of #3163 (comment) and write the explicit value of mod_inv_25 which is 0xc28f5c29 and replace the lines with:
const uint32_t mod_inv_25 = 0xc28f5c29 // = mod_inv_5 * mod_inv_5;

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vitaut commented May 17, 2023

Could you apply the alternative suggestion to suppress the warning? i.e.

const uint32_t mod_inv_25 = 0xc28f5c29 // = mod_inv_5 * mod_inv_5;

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The value of mod_inv_25 is now explicit in 32 and 64 bit:
const uint32_t mod_inv_25 = 0xc28f5c29; // = mod_inv_5 * mod_inv_5
const uint64_t mod_inv_25 = 0x8f5c28f5c28f5c29; // = mod_inv_5 * mod_inv_5

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vitaut commented May 18, 2023

Please rebase.

@florimond-collette florimond-collette changed the title revert non-working workaround for issue #3163 replace mod_inv_25 by explicit value as a fix for VS warning C4307 May 18, 2023
@vitaut vitaut merged commit d60b907 into fmtlib:master May 18, 2023
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vitaut commented May 18, 2023

Thanks

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