1. Introduction to the C Compiler
2. C-Compiler Implementation-Specific Information
2.3 Thread Local Storage Specifier
2.4 Floating Point, Nonstandard Mode
2.6.1 Printing long long Data Types
2.6.2 Usual Arithmetic Conversions
2.7 Case Ranges in Switch Statements
2.11.3 does_not_read_global_data
2.11.5 does_not_write_global_data
2.11.26 warn_missing_parameter_info
2.14.3 __inline and __inline__
2.14.5 __FUNCTION__ and __PRETTY_FUNCTION__
2.16 How to Specify Include Files
2.16.1 Using the -I- Option to Change the Search Algorithm
2.17 Compiling in Free-Standing Environments
7. Converting Applications for a 64-Bit Environment
8. cscope: Interactively Examining a C Program
A. Compiler Options Grouped by Functionality
B. C Compiler Options Reference
C. Implementation-Defined ISO/IEC C99 Behavior
E. Implementation-Defined ISO/IEC C90 Behavior
H. The Differences Between K&R Solaris Studio C and Solaris Studio ISO C
With -fast, the compiler is free to replace calls to floating point functions with equivalent optimized code that does not set the errno variable. Further, -fast also defines the macro __MATHERR_ERRNO_DONTCARE, which allows the compiler to ignore ensuring the validity of errno. As a result, user code that relies on the value of errno after a floating point function call could produce inconsistent results.
One way around this problem is to avoid compiling such codes with -fast. However, if -fast optimization is required and the code depends on the value of errno being set properly after floating-point library calls, you should compile with the options
-xbuiltin=none -U__MATHERR_ERRNO_DONTCARE -xnolibmopt -xnolibmil
following -fast on the command line to inhibit the compiler from optimizing out such library calls and to insure that errno is handled properly.