[llvm-commits] [llvm] r116920 - /llvm/trunk/include/llvm/Support/Compiler.h

[Chandler Carruth]

Author: chandlerc
Date: Wed Oct 20 03:44:27 2010
New Revision: 116920

URL: http://llvm.org/viewvc/llvm-project?rev=116920&view=rev
Log:
Add a comment about ATTRIBUTE_UNUSED to avoid further confusion over when to
use it.

Modified:
    llvm/trunk/include/llvm/Support/Compiler.h

Modified: llvm/trunk/include/llvm/Support/Compiler.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Compiler.h?rev=116920&r1=116919&r2=116920&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/Compiler.h (original)
+++ llvm/trunk/include/llvm/Support/Compiler.h Wed Oct 20 03:44:27 2010
@@ -31,6 +31,14 @@
 #define ATTRIBUTE_USED
 #endif
 
+// Some compilers warn about unused functions. When a function is sometimes
+// used or not depending on build settings (e.g. a function only called from
+// within "assert"), this attribute can be used to suppress such warnings.
+//
+// However, it shouldn't be used for unused *variables*, as those have a much
+// more portable solution:
+//   (void)unused_var_name;
+// Prefer cast-to-void wherever it is sufficient.
 #if (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
 #define ATTRIBUTE_UNUSED __attribute__((__unused__))
 #else