gcc compilation problem with -ansi option,

[Guruhema Prasad N]

Hi,

I am using redhatLinux8.0,  I am facing the following problems, can you 
please help any body.
Problem 1:-
 I am using option  "gcc -Wuninitialized -O -ansi", but its giving 
undeclared variables for the math defines "M_PI" which is defined in 
"/usr/include/math.h" file. If I remove "-ansi" option, its compiles 
properly, but I want to use "-ansi" option., I need to add any other 
options along with "-ansi"

Problem 2:-

Similarly, if I use "-ansi" option, I can't access the define "S_IFREG" 
in file "/usr/include/sys/stat.h".

Please suggest, what options I have to use along with "-ansi" to resolve 
above problems.

Thanks,

Guruhema