Re: Fix modification of string literal by swprintf

[Thomas Preudhomme <thomas.preudhomme@foss.arm.com>]

Hi Renlin,

Here's Silviu's answer:

"This happens when  --enable-newlib-mb is used (which wasn't in my test 
configuration).

Unfortunately this complicates thing a lot and I have no easy fix for it.
The best action at the moment would be a revert."

Corinna, could you revert the patch for now?

Sorry for the trouble. Best regards,

Thomas

On 14/06/17 12:05, Renlin Li wrote:
> Hi there,
>
> It seems this patch cause few regressions on arm/aarch64 baremetal targets.
>
> libstdc++-v3:
> FAIL: 21_strings/basic_string/numeric_conversions/wchar_t/dr1261.cc execution test
> FAIL: 21_strings/basic_string/numeric_conversions/wchar_t/stof.cc execution test
> FAIL: 21_strings/basic_string/numeric_conversions/wchar_t/to_wstring.cc
> execution test
> FAIL: 27_io/basic_ostream/inserters_arithmetic/wchar_t/4402.cc execution test
>
> newlib:
> FAIL: newlib.stdio/swprintf.c execution
>
> Regards,
> Renlin
>
> On 09/06/17 14:32, Corinna Vinschen wrote:
>> On Jun  8 13:15, Thomas Preudhomme wrote:
>>> Please find his updated patch attached.
>>>
>>> Best regards,
>>>
>>> Thomas
>>
>>> >From ee96a273969b0bccd308b81bcdf37a6fdefa06f6 Mon Sep 17 00:00:00 2001
>>> From: Silviu Baranga <silviu.baranga@arm.cm>
>>> Date: Mon, 5 Jun 2017 09:54:42 +0100
>>> Subject: [PATCH] Don't overread or write memory returned by _DTOA_R
>>>
>>> Don't over-read memory returned by _DTOA_R, and never write to it
>>> since the result might be a string literal.
>>>
>>> For example, when doing:
>>>    swprintf(tt, 20, L"%.*f", 6, 0.0);
>>>
>>> we will get back "0".
>>>
>>> Instead, write the result returned by _DTOA_R to the output buffer.
>>> After this, write the 0 chars directly to the the output buffer
>>> (if there are any). This also has the (marginal) advantage that
>>> we read/write less memory overall.
>>
>> Pushed.
>>
>>
>> Thanks,
>> Corinna
>>