Skip to content

Latest commit

 

History

History
121 lines (106 loc) · 4.29 KB

www-codingconventions.md

File metadata and controls

121 lines (106 loc) · 4.29 KB
Raw

wwwdocs PATCH Move part of gcc/README.Portability to codingconventions.html

This is mentioned as a FIXME under gcc/doc/sourcebuild.texi

I was not able to submit the patch with CVS (never used it before). At https://gcc.gnu.org/about.html#cvs it says:

cvs -q -d :ext:username@gcc.gnu.org:/cvs/gcc checkout -P wwwdocs where username is your user name at gcc.gnu.org

but I could not find know how to obtain such username.

This is the diff -u:

--- htdocs/codingconventions.html 2014-07-09 02:03:05.000000000 +0200 +++ codingconventions2.html 2015-05-16 11:49:39.000000000 +0200 @@ -30,8 +30,13 @@

  • Assertions
  • Character Testing

    •    <li><a href="#Empty_Macro_Arguments">Empty Macro Arguments</a></li>
   <li><a href="#Error">Error Node Testing</a></li>

    •    <li><a href="#Free_NULL_Check">Free NULL Check</a></li>

    •    <li><a href="#Long_Integer_Literal_Suffix">Long Integer Literal Suffix</a></li>
   <li><a href="#Generated">Parameters Affecting Generated Code</a></li>

    •    <li><a href="#Parenthesis_Around_String_Initializers">Parenthesis Around String Initializers</a></li>

    •    <li><a href="#Trigraphs">Trigraphs</a></li>
   <li><a href="#C_Inlining">Inlining Functions</a></li>
   </ul>

    @@ -708,6 +713,24 @@ language accepted.

    +

    Empty Macro Arguments

    + +

    ISO C (6.8.3 in the 1990 standard) specifies the following:

    + +
    If (before argument substitution) any argument consists of no +preprocessing tokens, the behavior is undefined.
    + +

    This was relaxed by ISO C99, but some older compilers emit an error, +so code like:

    + +
    
+#define foo(x, y) x y
+foo (bar, )
+
    + +

    needs to be coded in some other way.

    + +

    Error Node Testing

    Testing for ERROR_MARKs should be done by comparing @@ -716,12 +739,67 @@ href="https://gcc.gnu.org/ml/gcc-patches/2000-10/msg00792.html">message.

    +

    Free NULL Check

    + +

    Don't check if a pointer is NULL before freeing it.

    + +

    Since SunOS 4 stopped being a reasonable portability target, +(which happened around 2007) there has been no need to guard +against free (NULL). Thus, any guard like the following +constitutes a redundant test:

    + +
    
+if (P)
    

      

    • free (P);
+

+

However, if your profiling exposes a test like this in a +performance-critical loop, say where P is nearly always NULL, and +the cost of calling free on a NULL pointer would be prohibitively +high, consider using __builtin_expect, e.g., like this:

+ +

+if (__builtin_expect (ptr != NULL, 0))


    

  • free (ptr);
+

  • +

    Long Integer Literal Suffix

    + +

    Never use lower case l since it can be confused +with the number 1. Use upper case L instead.

    + +

    Parameters Affecting Generated Code

    Internal numeric parameters that may affect generated code should be controlled by --param rather than being hardcoded.

    +

    Parenthesis Around String Initializers

    + +

    Don't use parenthesis around string initializers.

    + +

    Irix6 cc -n32 and OSF4 cc have problems with +constant string initializers with parenthesis around it, e.g.:

    + +
    
+const char string[] = ("A string");
+
    + +

    This is unfortunate since this is what the GNU gettext macro N_ +produces. You need to find a different way to code it.

    + +

    Some compilers like MSVC++ have fairly low limits on the maximum +length of a string literal; 509 is the lowest we've come across. You +may need to break up a long printf statement into many smaller ones.

    + + +

    Trigraphs

    + +

    Don't use trigraphs because some compilers do not accept them.

    + +

    Inlining Functions