<para>

Sometimes it is useful to add compiler flags after-the-fact to the set

that were chosen by <filename>configure</>. An important example is

that <application>gcc</>'s <option>-Werror</> option cannot be included

in the <envar>CFLAGS</envar> passed to <filename>configure</>, because

it will break many of <filename>configure</>'s built-in tests. To add

such flags, include them in the <envar>COPT</envar> environment variable

while running <filename>make</>. The contents of <envar>COPT</envar>

are added to both the <envar>CFLAGS</envar> and <envar>LDFLAGS</envar>

options set up by <filename>configure</>. For example, you could do

<screen>

<userinput>make COPT='-Werror'</>

</screen>

or

<screen>

<userinput>export COPT='-Werror'</>

<userinput>make</>

</screen>

</para>

<para>

The <envar>COPT</> and <envar>PROFILE</> environment variables are

actually handled identically by the <productname>PostgreSQL</>

makefiles. Which to use is a matter of preference, but a common habit

among developers is to use <envar>PROFILE</> for one-time flag

adjustments, while <envar>COPT</> might be kept set all the time.

</para>