Article <v4es5k$29e2g$3@dont-email.me>

Warning: mysqli::__construct(): (HY000/1203): User howardkn already has more than 'max_user_connections' active connections in D:\Inetpub\vhosts\howardknight.net\al.howardknight.net\includes\artfuncs.php on line 21
Failed to connect to MySQL: (1203) User howardkn already has more than 'max_user_connections' active connections
Warning: mysqli::query(): Couldn't fetch mysqli in D:\Inetpub\vhosts\howardknight.net\al.howardknight.net\index.php on line 66
Article <v4es5k$29e2g$3@dont-email.me>

Deutsch English Français Italiano

<v4es5k$29e2g$3@dont-email.me>

View for Bookmarking (what is this?)
Look up another Usenet article

Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: "undefined behavior"?
Date: Thu, 13 Jun 2024 15:28:20 +0200
Organization: A noiseless patient Spider
Lines: 42
Message-ID: <v4es5k$29e2g$3@dont-email.me>
References: <666a095a$0$952$882e4bbb@reader.netnews.com>
 <v4d4hm$1rjc5$1@dont-email.me> <8734ph7qe5.fsf@nosuchdomain.example.com>
 <v4ddvg$1ta1b$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Thu, 13 Jun 2024 15:28:21 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="a4019a0b35be2744ae8acc392e7d37ca";
	logging-data="2406480"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18FiHB0PXmcW49OU3dS1mlH2mcaFnq2jHk="
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.11.0
Cancel-Lock: sha1:Q30t22wSd7xut7d73XWJdS4pkwg=
In-Reply-To: <v4ddvg$1ta1b$1@dont-email.me>
Content-Language: en-GB
Bytes: 2821

On 13/06/2024 02:19, Janis Papanagnou wrote:
> On 13.06.2024 00:22, Keith Thompson wrote:
>>
>> This:
>>      char outliers[100] = "";
>> initializes all 100 elements to zero.  So does this:
>>      char outliers[100] = { '\0' };
>> Any elements or members not specified in an initializer are set to zero.
> 
> Oops! This surprised me. (But you are right.) The overhead isn't
> [syntactically] obvious, but I'm anyway always setting a single
> '\0' character if I want to store strings in a 'char[]' and have
> it initialized to an empty string (like below).
> 
>> If you want to set an array's 0th element to 0 and not waste time
>> initializing the rest, you can assign it separately:
>>      char outliers[100];
>>      outliers[0] = '\0';
>> or
>>      char outliers[100];
>>      strcpy(outliers, "");
>> though the overhead of the function call is likely to outweigh the
>> cost of initializing the array.
> 
> It wouldn't occur to me to use the strcpy() function, but is the
> function call really that expensive in C ?
> 

That depends on your toolchain.

If you are using a Windows-based compiler with an external DLL for the C 
library and the compiler doesn't handle the strcpy() directly, then it 
can be quite a lot of overhead.  You have the call to the DLL, which 
involves a few steps of indirection.  The library strcpy() may be 
optimised for handling large strings, and may save and restore a lot of 
registers (such as SIMD vector registers).

If you are using a compiler (whatever the platform) that optimises 
"strcpy", it will generate identical code to "outliers[0] = '\0';".