src.sys.mk: Support src.conf in SRCTOP

If SRCCONF is not defined and src.conf exists at the top level of the
source tree, use that instead of /etc/src.conf.

MFC after:	3 days
Reviewed by:	kevans, imp
Differential Revision:	https://reviews.freebsd.org/D52470

(cherry picked from commit dd8c666d8b)

UPDATING: mention the src.conf change

Fixes:		dd8c666d8b ("src.sys.mk: Support src.conf in SRCTOP")
(cherry picked from commit ab2fea3f9a)

.gitignore

@@ -22,3 +22,4 @@ cscope.in.out
 cscope.out
 cscope.po.out
 tags
+/src.conf

UPDATING

@@ -17,6 +17,11 @@ and/or ports.
 	has changed.  An NFS server that exports any of these file systems will
 	need its clients to unmount and remount the exports.
 
+20250916:
+	If SRCCONF is unset and a file named src.conf is present at
+	the top of the source tree, it will now be used instead of
+	/etc/src.conf.
+
 20240419:
 	Clang, llvm, lld, lldb, compiler-rt, libc++, libunwind and openmp have
 	been upgraded to 18.1.6. It is important that you run `make delete-old`

share/man/man5/src.conf.5

@@ -1,6 +1,6 @@
 .\" DO NOT EDIT-- this file is @generated by tools/build/options/makeman.
 .\" $FreeBSD$
-.Dd March 8, 2024
+.Dd September 16, 2025
 .Dt SRC.CONF 5
 .Os
 .Sh NAME
@@ -30,8 +30,11 @@ variables that control the aspects of how the system builds.
 .Pp
 The default location of
 .Nm
-is
-.Pa /etc/src.conf ,
+is the top level of the source tree, or
+.Pa /etc/src.conf
+if no
+.Nm
+is found in the source tree itself,
 though an alternative location can be specified in the
 .Xr make 1
 variable

share/mk/src.sys.mk

@@ -6,7 +6,11 @@
 
 .if !defined(_WITHOUT_SRCCONF)
 # Allow user to configure things that only effect src tree builds.
+.if exists(${SRCTOP}/src.conf)
+SRCCONF?=	${SRCTOP}/src.conf
+.else
 SRCCONF?=	/etc/src.conf
+.endif
 .if !empty(SRCCONF) && \
     (exists(${SRCCONF}) || ${SRCCONF} != "/etc/src.conf") && \
     !target(_srcconf_included_)

sys/conf/kern.pre.mk

@@ -8,7 +8,11 @@
 # the rest of /usr/src, but they still always process SRCCONF even though
 # the normal mechanisms to prevent that (compiling out of tree) won't
 # work. To ensure they do work, we have to duplicate thee few lines here.
+.if exists(${SRCTOP}/src.conf)
+SRCCONF?=	${SRCTOP}/src.conf
+.else
 SRCCONF?=	/etc/src.conf
+.endif
 .if (exists(${SRCCONF}) || ${SRCCONF} != "/etc/src.conf") && !target(_srcconf_included_)
 .include "${SRCCONF}"
 _srcconf_included_:

tools/build/options/makeman

@@ -174,8 +174,11 @@ variables that control the aspects of how the system builds.
 .Pp
 The default location of
 .Nm
-is
-.Pa /etc/src.conf ,
+is the top level of the source tree, or
+.Pa /etc/src.conf
+if no
+.Nm
+is found in the source tree itself,
 though an alternative location can be specified in the
 .Xr make 1
 variable