I am reading a book called setting up LAMP and there is a section which teaches how to install mysql from source. The source files are to be compiled, but the compilation includes flags which I don't know what they are used for, and if they are really safe to use.

CFLAGS="-03"
CXX=gcc
CXXFLAGS="-03 -mpentiumpro -mstack-align-double -felide-constructors -fno-exceptions -fno-rtti"

# then the configure script

The book says that it's mandatory to use these flags and to have a newer compiler that understands them. If not, then the MySQL server could randomly crash. I am paranoid to use them, because I do not know exactly what they are meant to do.

Can someone please tell me which flags do what and if they are safe to use.

Thanks

Here's a description of all the gcc flags for the latest stable release (4.1.2) http://gcc.gnu.org/onlinedocs/gcc-4....Option-Summary.

those instructions may be valid in combination with the other optimizations used
in the book for the othr LAMP programms but only if you use exactly the versions used in the book and possibly with only the specific hardware used by the book writers.

you can give it a try one way or the other and give it some tests and if its going to be unstable you will know right away. mysql even comes with a test suite.
make test

what you posted there makes the book a bit suspect in my mind.

mostly the only necesary thing to add to the flags of mysql is
C_EXTRA_FLAGS=-fno-strict-aliasing

now the 64000 dollar question is if you need a rock solid server why not use debian or something
where the compiles have already been fully tested for both stability and security ?

building a server from scratch is not the greatest thing to be doing if you have to ask what the optimization flags do.