Change the default optimization level for Sun Studio to "-O1". 
This is a workaround for a Sun Studio bug (see bug #41710 
comments for details): 
 
1. Use $GCC instead of $ac_cv_prog_gcc to check for gcc, since 
the first one is the only documented way to do it. 
 
2. Use $GXX instead of $ac_cv_prog_cxx_g to check for g++, 
since the latter is set to "yes" when the C++ compiler accepts 
"-g" which is the case for both g++ and CC. 
 
3. When building with Sun Studio, set the default values for 
CFLAGS/CXXFLAGS to "-O1", since unlike GCC, Sun Studio 
interprets "-O" as "-xO3" (see the manual pages for cc and CC). 

configure.in:
  1. Use $GCC instead of $ac_cv_prog_gcc to check for gcc, since 
  the first one is the only documented way to do it. 
   
  2. Use $GXX instead of $ac_cv_prog_cxx_g to check for g++, 
  since the latter is set to "yes" when the C++ compiler accepts 
  "-g" which is the case for both g++ and CC. 
   
  3. When building with Sun Studio, set the default values for 
  CFLAGS/CXXFLAGS to "-O1", since unlike GCC, Sun Studio 
  interprets "-O" as "-xO3" (see the manual pages for cc and CC).