Fix crash via division by zero assertion #11508

pull jonasschnelli wants to merge 1 commits into bitcoin:master from jonasschnelli:2017/10/qt_cc_crash_zero changing 1 files +1 −2

jonasschnelli commented at 5:46 AM on October 16, 2017: contributor

Replaces the newly added assert for a devision by zero protection by a control structure. Floating point division by zero is defined by the floating point standard and results in +inf or -inf.

Introduced in #11133 Reported by @mzhou, fixes #11501
Fix crash via division by zero assertion 207408b088
jonasschnelli added the label GUI on Oct 16, 2017
meshcollider commented at 5:49 AM on October 16, 2017: contributor

utACK https://github.com/bitcoin/bitcoin/commit/207408b0889caf3f5986bde4b122dbece1ed0dac
practicalswift commented at 10:05 AM on October 16, 2017: contributor

ACK 207408b0889caf3f5986bde4b122dbece1ed0dac :-)

in src/qt/coincontroldialog.cpp:585 in 207408b088

 581 | @@ -582,8 +582,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
 582 |      QString toolTipDust = tr("This label turns red if any recipient receives an amount smaller than the current dust threshold.");
 583 |  
 584 |      // how many satoshis the estimated fee can vary per byte we guess wrong
 585 | -    assert(nBytes != 0);
 586 | -    double dFeeVary = (double)nPayFee / nBytes;
 587 | +    double dFeeVary = (nBytes != 0) ? (double)nPayFee / nBytes : 0;

promag commented at 1:18 PM on October 17, 2017:

Nit, like above in line 567:

double dFeeVary = nBytes > 0 ? (double)nPayFee / nBytes : 0;

promag commented at 1:19 PM on October 17, 2017: member

utACK 207408b.
laanwj commented at 1:21 PM on October 18, 2017: member

utACK 207408b

Floating point division by zero is defined by the floating point standard and results in +inf or -inf.

Indeed, floating point division by zero is well-defined in IEEE 754 which all current platforms (certainly the ones bitcoind runs on) implement.
laanwj merged this on Oct 18, 2017
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#11133 Document assumptions that are being made to avoid division by zero #11501 Assertion fail when opening coin control dialog