Databases
StackOverflow2013
Postsdbo
POIs it required to check a pointer validity if new fails?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POIs it required to check a pointer validity if new fails?
    primarykey
    data
    text
    <p>As title says, i know that new throws an exception which can be caught, but what exactly happens to the pointer? it turns NULL? I checked some answers on SO but none explained it. Check example below, the pointer keeps on the heap? please give full info on this pattern</p> <pre><code>#include &lt;windows.h&gt; #include &lt;cstdlib&gt; #include &lt;iostream&gt; using namespace std; enum eReadMode { // READ_ONLY, READ_WRITE, // CREATE_FILE, // CREATE_WRITE_FILE, }; class CFileStatic { private: FILE *m_File; public: CFileStatic( LPCTSTR szFileName, eReadMode eMode ); virtual ~CFileStatic() {}; bool IsValidFile() const { return( m_File != NULL ); }; void PrintFile( unsigned int uLine = 0 ); }; CFileStatic::CFileStatic( LPCTSTR szFileName, eReadMode eMode ) { if( szFileName ) { if( eMode == READ_WRITE ) m_File = fopen( szFileName, "r+" ); else printf( "Valid usage of: READ_WRITE only" ); } else m_File = NULL; } void CFileStatic::PrintFile( unsigned int uLine ) { static unsigned uFindNumber; if( uLine == 0 ) { char szBuffer[1024]; while( fgets( szBuffer, 1024, m_File ) ) { std::cout &lt;&lt; szBuffer; } } else { char szBuffer[1024]; while( fgets( szBuffer, 1024, m_File ) ) { uFindNumber++; if( uFindNumber == uLine ) { std::cout &lt;&lt; szBuffer; } } } } int main( int argc, char *argv[] ) { //if new fails, what 'pFile' turns out to be? and do I need to delete //it later? CFileStatic *pFile = new CFileStatic( "Console.h", READ_WRITE ); if( pFile-&gt;IsValidFile() ) { pFile-&gt;PrintFile(2); } CFileStatic *pConsoleCpp = new CFileStatic( "Console.cpp", READ_WRITE ); if( pConsoleCpp-&gt;IsValidFile() ) { pConsoleCpp-&gt;PrintFile(); } system("pause&gt;nul"); return EXIT_SUCCESS; } </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USZeta
    1. USVinicius Horta
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POIs it required to check a pointer validity if new fails?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POIs it required to check a pointer validity if new fails?
      1. USVinicius Horta
      1. VTFavorite
    1. CO`pFile` remains uninitialized, as the exception prevents the assignment from ever happening.
      singulars
      1. POIs it required to check a pointer validity if new fails?
      1. USErik
    2. COAh I see, so it doesn't initialize anything, so nothing is on the heap. Thanks guys that's exactly what I needed to know, please close the question ^^
      singulars
      1. POIs it required to check a pointer validity if new fails?
      1. USVinicius Horta
    3. COOh I see, thanks!
      singulars
      1. POIs it required to check a pointer validity if new fails?
      1. USVinicius Horta
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload