diff --git a/pcp-configure-c99.patch b/pcp-configure-c99.patch
new file mode 100644
index 0000000..aea9186
--- /dev/null
+++ b/pcp-configure-c99.patch
@@ -0,0 +1,68 @@
+Avoid calling the undeclared exit function.  Include <string.h> for
+strcmp.  Improves compatibility with future compilers which are likely
+to reject implicit function declarations by default.
+
+Submitted upstream:
+
+  <https://github.com/performancecopilot/pcp/pull/1727>
+
+diff --git a/configure b/configure
+index d8726f045b264191..f285191756825493 100755
+--- a/configure
++++ b/configure
+@@ -14409,7 +14409,7 @@ main ()
+ {
+ 
+     double x = 123.456;
+-    if (fpclassify(x) == FP_NAN) exit(1);
++    if (fpclassify(x) == FP_NAN) return 1;
+ 
+   ;
+   return 0;
+@@ -14438,7 +14438,7 @@ main ()
+ {
+ 
+     double x = 123.456;
+-    if (fpclassify(x) == FP_NAN) exit(1);
++    if (fpclassify(x) == FP_NAN) return 1;
+ 
+   ;
+   return 0;
+@@ -16433,6 +16433,7 @@ else
+ /* end confdefs.h.  */
+ 
+ #include <time.h>
++#include <string.h>
+ int main () {
+     char b[32]="";
+     time_t t = time(NULL);
+diff --git a/configure.ac b/configure.ac
+index f12e652dd5e6f20e..4f737c78ff63e670 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -3097,7 +3097,7 @@ AC_TRY_LINK(
+ ],
+ [
+     double x = 123.456;
+-    if (fpclassify(x) == FP_NAN) exit(1);
++    if (fpclassify(x) == FP_NAN) return 1;
+ ], ac_cv_func_fpclassify=yes)
+ AC_MSG_RESULT($ac_cv_func_fpclassify)
+ if test $ac_cv_func_fpclassify = no
+@@ -3112,7 +3112,7 @@ then
+ ],
+ [
+     double x = 123.456;
+-    if (fpclassify(x) == FP_NAN) exit(1);
++    if (fpclassify(x) == FP_NAN) return 1;
+ ], ac_cv_func_fpclassify=yes)
+     AC_MSG_RESULT($ac_cv_func_fpclassify)
+     if test $ac_cv_func_fpclassify = yes
+@@ -3737,6 +3737,7 @@ AC_MSG_CHECKING([if strftime knows about %z])
+ AC_TRY_RUN(
+ [
+ #include <time.h>
++#include <string.h>
+ int main () {
+     char b[32]="";
+     time_t t = time(NULL);
diff --git a/pcp.spec b/pcp.spec
index f76dd9c..f5823ef 100644
--- a/pcp.spec
+++ b/pcp.spec
@@ -1,12 +1,13 @@
 Name:    pcp
 Version: 6.0.1
-Release: 3%{?dist}
+Release: 4%{?dist}
 Summary: System-level performance monitoring and performance management
 License: GPLv2+ and LGPLv2+ and CC-BY
 URL:     https://pcp.io
 
 %global  artifactory https://performancecopilot.jfrog.io/artifactory
 Source0: %{artifactory}/pcp-source-release/pcp-%{version}.src.tar.gz
+Patch0: pcp-configure-c99.patch
 
 # The additional linker flags break out-of-tree PMDAs.
 # https://bugzilla.redhat.com/show_bug.cgi?id=2043092
@@ -2286,7 +2287,7 @@ updated policy package.
 
 
 %prep
-%setup -q
+%autosetup -p1
 
 %build
 # the buildsubdir macro gets defined in %%setup and is apparently only available in the next step (i.e. the %%build step)
@@ -3371,6 +3372,9 @@ fi
 %files zeroconf -f pcp-zeroconf-files.rpm
 
 %changelog
+* Mon Dec 12 2022 Florian Weimer <fweimer@redhat.com> - 6.0.1-4
+- Port configure script to C99
+
 * Thu Nov 03 2022 Jiri Olsa <jolsa@kernel.org> - 6.0.1-3
 - rebuilt for libbpf 1.0