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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: Small Device C Compiler 3.6.0 released
Date: Thu, 16 Jun 2016 09:07:54 -0700
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David Brown <david.brown@hesbynett.no> writes:
> On 16/06/16 14:06, BartC wrote:
[...]
>> I've looked at some more aspects of block-scopes. If I try this code:
>> 
>> {
>>     int* p;
>>     {
>>         int A = 77;
>>         p = &A;
>>     }
>>     printf("*p=%d\n", *p);
>> }
>> 
>> then none of compilers I tried gives any sort of warning about it. (That
>> is, Pelles C, lccwin, DMC, gcc, TCC and clang. gcc was given -Wall
>> -Wextra -Wpedantic and the output was not filtered.)
>
> gcc warns about it - though the warning is the slightly cryptic
> "warning: 'A' is used uninitialized in this function".

gcc-5.2.0 and up print that warning.  gcc-4.9.0 does not.  Also, with
gcc-4.9.0 and earlier, the output is "*p=77" at all optimization levels.

[...]

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"