configure: Abort if gperf is not found but generated files don't exist

When building from a tarball gperf is not required as the generated
files already exist, however, when building from the repository that's
not the case, so warn the user if gperf is not found.

diff --git a/configure.ac b/configure.ac
index 329739d..83918ad 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -378,7 +378,7 @@ AC_ARG_VAR([PERL], [the Perl interpreter])
 AC_PATH_PROG([GPERF], [gperf], [], [$PATH:/bin:/usr/bin:/usr/local/bin])
 AC_ARG_VAR([GPERF], [the GNU gperf program])
 
-# because gperf is not needed by end-users we just report it but do not abort on failure
+# because gperf is not needed by end-users we only abort if generated files don't exist
 AC_MSG_CHECKING([gperf version >= 3.0.0])
 if test -x "$GPERF"; then
        if test "`$GPERF --version | $AWK -F' ' '/^GNU gperf/ { print $3 }' | $AWK -F. '{ print $1 }'`" -ge "3"; then
@@ -403,6 +403,10 @@ if test -x "$GPERF"; then
        fi
 else
        AC_MSG_RESULT([not found])
+       GPERF_TEST_FILE="$srcdir/src/libstrongswan/crypto/proposal/proposal_keywords_static.c"
+       if test ! -f "$GPERF_TEST_FILE"; then
+               AC_MSG_ERROR([GNU gperf required to generate e.g. $GPERF_TEST_FILE])
+       fi
 fi
 
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