C / C++: Difference between revisions

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See also [[C]] and [[C++]].

== C ==
== C ==
=== References ===
=== References ===
Line 80: Line 82:
See also [[C / C++#C|C reference above]].
See also [[C / C++#C|C reference above]].


<ul>
* [http://www.cplusplus.com/reference/ www.cplusplus.com &mdash; C++ Reference]
** Including [http://www.cplusplus.com/reference/clibrary/ C Language Library]
<li>[http://www.cplusplus.com/reference/ www.cplusplus.com &mdash; C++ Reference]</li>
** and ... [http://www.cplusplus.com/reference/iostream/ IOStream Library]
* Including [http://www.cplusplus.com/reference/clibrary/ C Language Library]
* [http://www.sgi.com/tech/stl/ SGI &mdash; Standard Template Library Programmer's Guide]
* and ... [http://www.cplusplus.com/reference/iostream/ IOStream Library]
<li> [http://www.sgi.com/tech/stl/ SGI &mdash; Standard Template Library Programmer's Guide]</li>
* manpage <tt>stl-manual</tt> (from SGI)
<li> [http://www.research.att.com/~bs/hopl-almost-final.pdf Evolving a language in and for the real world: C++ 1991-2006, Bjarne Stroustrup] (pdf)</li>
<li> manpage <tt>stl-manual</tt> (from SGI)</li>
<source lang="bash">
<source lang="bash">
sudo apt-get install stl-manual
sudo apt-get install stl-manual
ln -s /usr/share/doc/stl-manual/html /var/www/sgi # Now the manual is available at http://localhost/sgi
ln -s /usr/share/doc/stl-manual/html /var/www/sgi # Now the manual is available at http://localhost/sgi
</source>
</source>
</ul>


Make a local copy:
=== References - local copy ===
<source lang="bash">
<source lang="bash">
# Make a local copy of www.cplusplus.com - use option -P http://proxy:port if needed
# Make a local copy of www.cplusplus.com - use option -P http://proxy:port if needed
Line 96: Line 101:
</source>
</source>


=== Benchmark ===
==== Between compilers ====
* '''g++'''
* '''[http://www.phoronix.com/scan.php?page=article&item=pathscale_ekopath4_open&num=1 EKOPath4]''', a recently open-sourced compiler with much better performance than gcc/g++.
* '''Intel compiler'''
* '''pathCC''', PathScale compiler

==== Between languages ====
* C++ reported to be the ''fastest language'', even faster than C and java. See [http://shootout.alioth.debian.org/ The Computer Language Benchmarks Game]
*[http://developers.slashdot.org/story/11/06/15/0242237/C-the-Clear-Winner-In-Googles-Language-Performance-Tests C++ the Clear Winner In Google's Language Performance Tests]

=== Nested Classes ===
See [http://publib.boulder.ibm.com/infocenter/comphelp/v8v101/index.jsp?topic=%2Fcom.ibm.xlcpp8a.doc%2Flanguage%2Fref%2Fcplr061.htm Nested classes on ibm.com].

=== Tips ===

{| class=wikitable width="100%"
!Problem
!width="600px"|Solution
|-
|Overloading operators <code>i++</code> or <code>++i</code><br/>See [http://www.parashift.com/c++-faq-lite/operator-overloading.html#faq-13.14] for more details.
|

{{nb|<source lang="c">
class Number {
public:
// prefix ++ - Must return (*this)
Number& operator++ ();
// postfix ++ - Must never return (*this) by reference
Number operator++ (int); // ... OR ....
void operator++ (int);
};
</source>}}
|-
|Reset <code>ostringstream</code>
|
{{nb|<source lang="c">
ostringstream oss;
oss << "Hello," << 123 << endl;
string s = oss.str();

oss.str(""); // oss empty now - we can reuse it
oss << "World!" << 456 << endl;
</source>}}
|}

=== Security Tips ===

{| class=wikitable width="100%"
!Problem
!width="600px"|Solution
|-
| Use <code>mlock()</code> to prevent a section of memory from swapping to disk<br/>(source: "Building Secure Software," John Viega & Gary McGraw)
|
|}

=== Tools ===
==== GNU cflow ====
'''GNU cflow''' analyzes a collection of C source files and prints a graph, charting control flow within the program.

GNU cflow is able to produce both direct and inverted flowgraphs for C sources. Optionally a cross-reference listing can be
generated. Two output formats are implemented: POSIX and GNU (extended).


=== &lt;iostream.h&gt; or &lt;iostream&gt; ===
=== &lt;iostream.h&gt; or &lt;iostream&gt; ===

Latest revision as of 15:19, 15 July 2021

See also C and C++.

C

References

sudo apt-get install manpages-dev manpages-posix-dev

Tips

Variadic Macros

See reference here.

#define eprintf(...) fprintf (stderr, __VA_ARGS__)
/* eprintf ("%s:%d: ", input_file, lineno)
          ==>  fprintf (stderr, "%s:%d: ", input_file, lineno) */
#define eprintf(args...) fprintf (stderr, args)
#define eprintf(format, ...) fprintf (stderr, format, __VA_ARGS__)

An handy macro hack that counts the number of parameters passed before expansion (See [1] and [2]):

 /* The PP_NARG macro returns the number of arguments that have been
  * passed to it. This compensates for lack of __VA_NARGS__.
  * Macros written by Laurent Deniau See http://en.wikipedia.org/wiki/Variadic_macro.
  */ 

#define PP_NARG(...) \ 
         PP_NARG_(__VA_ARGS__,PP_RSEQ_N()) 
#define PP_NARG_(...) \ 
         PP_ARG_N(__VA_ARGS__) 
#define PP_ARG_N( \ 
          _1, _2, _3, _4, _5, _6, _7, _8, _9,_10, \ 
         _11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \ 
         _21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \ 
         _31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \ 
         _41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \ 
         _51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \ 
         _61,_62,_63,N,...) N 
#define PP_RSEQ_N() \ 
         63,62,61,60,                   \ 
         59,58,57,56,55,54,53,52,51,50, \ 
         49,48,47,46,45,44,43,42,41,40, \ 
         39,38,37,36,35,34,33,32,31,30, \ 
         29,28,27,26,25,24,23,22,21,20, \ 
         19,18,17,16,15,14,13,12,11,10, \ 
         9,8,7,6,5,4,3,2,1,0 

/* Some test cases */ 
PP_NARG(A) -> 1 
PP_NARG(A,B) -> 2 
PP_NARG(A,B,C) -> 3 
PP_NARG(A,B,C,D) -> 4 
PP_NARG(A,B,C,D,E) -> 5 
PP_NARG(1,2,3,4,5,6,7,8,9,0, 
         1,2,3,4,5,6,7,8,9,0, 
         1,2,3,4,5,6,7,8,9,0, 
         1,2,3,4,5,6,7,8,9,0, 
         1,2,3,4,5,6,7,8,9,0, 
         1,2,3,4,5,6,7,8,9,0, 
         1,2,3) -> 63

Temporary variable names for Macro

/* UNIQ(x) creates a unique variable name that depends on the current source line as returned by __LINE__. We need
   Several intermediate macros because identifier are not expanded in macro if they are used along with # or ## in
   macro definition.

   Example:   #define SCAN_MY(var,n)   {int UNIQ(x); for(UNIQ(x)=0; UNIQ(x)<n; ++UNIQ(x)) printf(var[UNIQ(x)]);}
*/
#define UNIQ__(x,y) x ## y
#define UNIQ_(x,y)  UNIQ__(x,y)
#define UNIQ(x)     UNIQ_(x,__LINE__)

C++

References

See also C reference above.

References - local copy

# Make a local copy of www.cplusplus.com - use option -P http://proxy:port if needed
httrack http://www.cplusplus.com/ -W -O /var/www -%v "-www.cplusplus.com/forum/*" "-www.cplusplus.com/src/*" "-www.cplusplus.com/member/*"

Benchmark

Between compilers

  • g++
  • EKOPath4, a recently open-sourced compiler with much better performance than gcc/g++.
  • Intel compiler
  • pathCC, PathScale compiler

Between languages

Nested Classes

See Nested classes on ibm.com.

Tips

Problem Solution
Overloading operators i++ or ++i
See [3] for more details.
class Number {
public:
    // prefix ++ - Must return (*this)
    Number& operator++ ();    
    // postfix ++ - Must never return (*this) by reference
    Number  operator++ (int);  // ... OR ....
    void  operator++ (int);   
};
Reset ostringstream
ostringstream oss;
oss << "Hello," << 123 << endl;
string s = oss.str();

oss.str("");                  // oss empty now - we can reuse it
oss << "World!" << 456 << endl;

Security Tips

Problem Solution
Use mlock() to prevent a section of memory from swapping to disk
(source: "Building Secure Software," John Viega & Gary McGraw)

Tools

GNU cflow

GNU cflow analyzes a collection of C source files and prints a graph, charting control flow within the program.

GNU cflow is able to produce both direct and inverted flowgraphs for C sources. Optionally a cross-reference listing can be generated. Two output formats are implemented: POSIX and GNU (extended).

<iostream.h> or <iostream>

  • <iostream> is the standard compliant library. <iostream.h> is deprecated since many many years.
  • <iostream> contains a set of templatized I/O classes which support both narrow and wide characters (by contrast, <iostream.h> classes are confined to char exclusively).
  • Third, the C++ standard specification of iostream's interface was changed in many subtle aspects. Consequently, the interfaces and implementation of <iostream> differ from <iostream.h>.
  • Finally, <iostream> components are declared in namespace std whereas <iostream.h> components are declared in the global scope.

Note that both libraries cannot be mixed in one program.