c - Why it is not an error to increment array "a" in the below function? -

- 

#include<stdio.h> void printd(char []); int main(void){        char a[100];        a[0]='a';a[1]='b';a[2]='c';a[4]='d';        printd(a);        return 0; } void printd(char a[]){         a++;         printf("%c",*a);         a++;         printf("%c",*a); }

explanation: expecting result in lvalue error. working out error , giving bc output. why incrementing array "a" not error?

if array passed function decays pointer array's first element.

due inside printd() pointer a can incremented , decremented, point different elements of array a defined in main().

please note when declaring/defining function's parameter list type t expression t[] equivaltent t*.

in question's specific case

void printd(char a[]);

is same as

void printd(char * a);

the code below shows equivalent behaviour op's code, pa behaving a in side printd():

#include <stdio.h>  int main(void) {    char a[100];    a[0]='a';a[1]='b';a[2]='c';a[4]='d';     {      char * pa = a;       pa++;      printf("%c", *pa);      pa++;      printf("%c", *pa);    }     return 0; `}

Comments

Post a Comment

Popular posts from this blog

python - jinja2: TemplateSyntaxError: expected token ',', got 'string' -

-
i new jinja2 , having issue using python regular expression (re). in following code bold lines have error string in them. {% block content %} <div class="container"> {% l in lines %} {% if re.search(r"error", l) %} {# <<< throws error #} <b> {{ l }} </b> {% else %} {{ l }} <hr> {% endif %} {% endfor %} </div> {% endblock %} the re.search above throws following error: jinja2.exceptions.templatesyntaxerror templatesyntaxerror: expected token ',', got 'string' raw python code not supported in jinja2 template syntax. {% if re.search(r"error", l) %} replace line with {% if "error" in l %} can fix problem. if logical condition more complicated, should consider defining own custom filters (which can call python code) or complicated things in view layer. go check global namespace .
Read more

node.js - NodeJS remote terminal to Dropbear OpenWRT-Server -

-
i wandering whether there valid solution have remote terminal openwrt-box out of nodejs-app? connecting terminal works: ssh -i ~/.mykeys/id_rsa root@192.168.178.39 busybox v1.23.2 (2015-04-22 23:25:48 utc) built-in shell (ash) root@openwrt:~# the only interactive ssh solution nodejs doesn't interactive part described in readme.md following: var client = require('ssh2').client; var conn = new client(); conn.on('ready', function() { console.log('client :: ready'); conn.shell(function(err, stream) { if (err) throw err; stream.on('close', function() { console.log('stream :: close'); conn.end(); }).on('data', function(data) { console.log('stdout: ' + data); }).stderr.on('data', function(data) { console.log('stderr: ' + data); }); stream.end('ls -l\nexit\n'); }); }).connect({ host: '192.168.100.100', port: 22, username...
Read more

Qt4: how to send QString inside a struct via QSharedMemory -

-
i have struct struct control_data{ int column_number; qstring cell; }; i need send thread of qsharememory. read can't because qstring contains pointers inside. other ways? you have serialize struct byte array. can convert qstring const char* this: mystring.tostdstring().c_str(); but serializing qstring should work. the first step serialize struct qdatastream using qt, example here . then once struct can read , written can pass shared memory. a complete example of using qsharedmemory can found here . here relevant code: // first, test whether shared memory segment attached process. // if so, detach if (sharedmem.isattached()) { sharedmem.detach(); } ... qbuffer buffer; buffer.open( qbuffer::readwrite ); qdatastream out( &buffer ); out << youstruct; int size = buffer.size(); // size of int + size of qstring in bytes if ( !sharedmem.create( size ) ) { return; } // write shared memory sharedmem.lock(); char *to = (char*...
Read more