git: e89d737041d1 - main - config.5: Document CONF_CFLAGS under 'makeoptions'

The branch main has been updated by olce:

URL: https://cgit.FreeBSD.org/src/commit/?id=e89d737041d15d8b3763c2829ee97dc8fcc69cbc

commit e89d737041d15d8b3763c2829ee97dc8fcc69cbc
Author:     Olivier Certner <olce@FreeBSD.org>
AuthorDate: 2025-05-27 07:41:19 +0000
Commit:     Olivier Certner <olce@FreeBSD.org>
CommitDate: 2025-05-27 07:59:05 +0000

    config.5: Document CONF_CFLAGS under 'makeoptions'
    
    This variable serves to tweak CFLAGS from the kernel configuration file,
    easing some custom kernel builds.  It was introduced by bde@ in 1999.
---
 usr.sbin/config/config.5 | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/usr.sbin/config/config.5 b/usr.sbin/config/config.5
index 93d65819d1d8..246e20c081ae 100644
--- a/usr.sbin/config/config.5
+++ b/usr.sbin/config/config.5
@@ -316,11 +316,27 @@ variable is specified,
 .Ar value
 is assumed to be the empty string.
 .Pp
+Note that, as the common makefiles override the
+.Va CFLAGS
+variable after having processed the configuration file,
+customizing
+.Va CFLAGS
+directly via
+.Ic makeoptions
+is not possible.
+However, custom compiler flags can be specified using the
+.Va CONF_CFLAGS
+variable.
+They are appended after most of the flags automatically going into
+.Va CFLAGS ,
+allowing to override those that are not essential to the build process.
+.Pp
 Example:
 .Bd -literal -offset indent -compact
 makeoptions MYMAKEOPTION="foo"
 makeoptions MYMAKEOPTION+="bar"
 makeoptions MYNULLMAKEOPTION
+makeoptions CONF_CFLAGS+="-DSOME_CONTROLLING_MACRO"
 .Ed
 .\" -------- MAXUSERS --------
 .Pp