Date: Fri, 10 Jan 2003 15:39:21 -0800 From: Marcel Moolenaar <marcel@xcllnt.net> To: arch@FreeBSD.org Cc: ru@FreeBSD.org Subject: Infinite loop in make(1) Message-ID: <20030110233921.GA1381@athlon.pn.xcllnt.net>
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Gang,
During release building we hit upon an infinite loop in make(1).
This was cause by a substitution of which the LHS and RHS were
both empty and the substitution was to be applied globally.
For example (from ports/devel/m6811-gcc/Makefile):
CFLAGS := ${CFLAGS:S/${_CPUCFLAGS}//g}
If ${_CPUCFLAGS} is empty, the expansion obviously yields S///g.
This causes make(1) to enter an infinite loop.
Below a patch to prevent the infinite loop by forcing non-global
substitution. This still allows S/^/foo/ and S/$/bar/ and even
S///, but avoids the danger zone.
Is this correct?
\begin{patch}
Index: var.c
===================================================================
RCS file: /home/ncvs/src/usr.bin/make/var.c,v
retrieving revision 1.40
diff -u -r1.40 var.c
--- var.c 8 Nov 2002 16:59:11 -0000 1.40
+++ var.c 10 Jan 2003 23:30:58 -0000
@@ -1349,6 +1349,17 @@
cp++;
}
+ /*
+ * Replacing the empty string for something else when
+ * done globally causes an infinite loop. The only
+ * meaningful substitution of the empty string would
+ * be those anchored by '^' or '$'. Thus, we can
+ * safely turn the substitution into a non-global one
+ * if the LHS is the empty string.
+ */
+ if (pattern.leftLen == 0)
+ pattern.flags &= ~VAR_SUB_GLOBAL;
+
termc = *cp;
newStr = VarModify(str, VarSubstitute,
(void *)&pattern);
\end{patch}
--
Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
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