Closes #61

Author: jkbzh

Changelog

@@ -6,6 +6,9 @@ HYPERMAIL VERSION 2.4.1:
 ============================
 
 2020-06-12 Jose Kahan
+	* configure.ac
+	configure didn't signal an error if yacc was not installed
+
 	* src/parse.c
 	URLs were not detected and converted when they were preceeded by a :
 	that was not attached to a valid URL like foo: https://example.com or :

configure

@@ -709,6 +709,7 @@ LN_S
 INSTALL_DATA
 INSTALL_SCRIPT
 INSTALL_PROGRAM
+YACC_CHECK
 YFLAGS
 YACC
 CPP
@@ -3444,6 +3445,46 @@ fi
 done
 test -n "$YACC" || YACC="yacc"
 
+# Extract the first word of "$YACC", so it can be a program name with args.
+set dummy $YACC; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_YACC_CHECK+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$YACC_CHECK"; then
+  ac_cv_prog_YACC_CHECK="$YACC_CHECK" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_YACC_CHECK="yes"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+YACC_CHECK=$ac_cv_prog_YACC_CHECK
+if test -n "$YACC_CHECK"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $YACC_CHECK" >&5
+$as_echo "$YACC_CHECK" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+if test x"$YACC_CHECK" != x"yes"; then :
+  as_fn_error $? "Please install either bison or yacc and run configure again" "$LINENO" 5
+fi
 # Find a good install program.  We prefer a C program (faster),
 # so one script is as good as another.  But avoid the broken or
 # incompatible versions:

configure.ac

@@ -46,6 +46,8 @@ dnl ===========================================================================
 AC_PROG_CC
 AC_PROG_CPP
 AC_PROG_YACC
+AC_CHECK_PROG(YACC_CHECK,$YACC,yes)
+AS_IF([test x"$YACC_CHECK" != x"yes"], [AC_MSG_ERROR([Please install either bison or yacc and run configure again])])
 AC_PROG_INSTALL
 AC_PROG_LN_S
 AC_PROG_MAKE_SET