[llvm] r185397 - [APFloat] Ensure that we can properly parse strings that do not have null terminators.

[Eli Friedman]

On Mon, Jul 1, 2013 at 4:54 PM, Michael Gottesman <mgottesman at apple.com>wrote:

> Author: mgottesman
> Date: Mon Jul  1 18:54:08 2013
> New Revision: 185397
>
> URL: http://llvm.org/viewvc/llvm-project?rev=185397&view=rev
> Log:
> [APFloat] Ensure that we can properly parse strings that do not have null
> terminators.
>
> rdar://14323230
>
> Modified:
>     llvm/trunk/lib/Support/APFloat.cpp
>     llvm/trunk/unittests/ADT/APFloatTest.cpp
>
> Modified: llvm/trunk/lib/Support/APFloat.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APFloat.cpp?rev=185397&r1=185396&r2=185397&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Support/APFloat.cpp (original)
> +++ llvm/trunk/lib/Support/APFloat.cpp Mon Jul  1 18:54:08 2013
> @@ -2481,7 +2481,14 @@ APFloat::convertFromDecimalString(String
>             42039/12655 < L < 28738/8651  [ numerator <= 65536 ]
>    */
>
> -  if (decDigitValue(*D.firstSigDigit) >= 10U) {
> +  // Test if we have a zero number allowing for strings with no null
> terminators
> +  // and zero decimals with non-zero exponents.
> +  //
> +  // We computed firstSigDigit by ignoring all zeros and dots. Thus if
> +  // D->firstSigDigit equals str.end(), every digit must be a zero and
> there can
> +  // be at most one dot. On the other hand, if we have a zero with a
> non-zero
> +  // exponent, then we know that D.firstSigDigit will be non-numeric.
> +  if (decDigitValue(*D.firstSigDigit) >= 10U || D.firstSigDigit ==
> str.end()) {
>      category = fcZero;
>      fs = opOK;
>
>
Aren't these checks in the wrong order?  It would be nice to avoid
dereferencing str.end().

-Eli
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