Update copyright years.

[thirdparty/gcc.git] / gcc / README.Portability

diff --git a/gcc/README.Portability b/gcc/README.Portability
index 32a33e27bec854a4d6b9468008751ba47a632bb1..cd03da7216008b8ca8e2149b2d22dd96007d7b7d 100644 (file)
--- a/gcc/README.Portability
+++ b/gcc/README.Portability
@@ -1,4 +1,4 @@
-Copyright (C) 2000, 2003 Free Software Foundation, Inc.
+Copyright (C) 2000-2022 Free Software Foundation, Inc.

 
 This file is intended to contain a few notes about writing C code
 within GCC so that it compiles without error on the full range of
 
 This file is intended to contain a few notes about writing C code
 within GCC so that it compiles without error on the full range of


@@ -6,7 +6,7 @@ compilers GCC needs to be able to compile on.
 
 The problem is that many ISO-standard constructs are not accepted by
 either old or buggy compilers, and we keep getting bitten by them.
 
 The problem is that many ISO-standard constructs are not accepted by
 either old or buggy compilers, and we keep getting bitten by them.

-This knowledge until know has been sparsely spread around, so I
+This knowledge until now has been sparsely spread around, so I

 thought I'd collect it in one useful place.  Please add and correct
 any problems as you come across them.
 
 thought I'd collect it in one useful place.  Please add and correct
 any problems as you come across them.
 


@@ -21,14 +21,6 @@ http://gcc.gnu.org/codingconventions.html
 String literals
 ---------------
 
 String literals
 ---------------
 

-Irix6 "cc -n32" and OSF4 "cc" have problems with constant string
-initializers with parens 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.
 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.


@@ -51,14 +43,28 @@ foo (bar, )
 needs to be coded in some other way.
 
 
 needs to be coded in some other way.
 
 

-free and realloc
-----------------
+Avoid unnecessary test before free
+----------------------------------
+
+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:

 
 

-Some implementations crash upon attempts to free or realloc the null
-pointer.  Thus if mem might be null, you need to write
+  if (P)
+    free (P);
+
+It is better to avoid the test.[*]
+Instead, simply free P, regardless of whether it is NULL.
+
+[*] 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);

 
 

-  if (mem)
-    free (mem);

 
 
 Trigraphs
 
 
 Trigraphs


@@ -194,4 +200,3 @@ o Passing incorrect types to fprintf and friends.
 
 o Adding a function declaration for a module declared in another file to
   a .c file instead of to a .h file.
 
 o Adding a function declaration for a module declared in another file to
   a .c file instead of to a .h file.

-