tool_getparam: clear argument only when needed

Test 699 verifies

Reported-by: bsr13 on hackerone
Closes #17112

src/tool_getparam.c

@@ -1785,7 +1785,8 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
         nextarg = &parse[1]; /* this is the actual extra parameter */
         singleopt = TRUE;   /* do not loop anymore after this */
 #ifdef HAVE_WRITABLE_ARGV
-        clearthis = &cleararg1[parse + 2 - flag];
+        if(cleararg1)
+          clearthis = &cleararg1[parse + 2 - flag];
 #endif
       }
       else if(!nextarg) {
@@ -1794,7 +1795,8 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
       }
       else {
 #ifdef HAVE_WRITABLE_ARGV
-        clearthis = cleararg2;
+        if(cleararg2)
+          clearthis = cleararg2;
 #endif
         *usedarg = TRUE; /* mark it as used */
       }

tests/data/Makefile.am

@@ -101,8 +101,7 @@ test654 test655 test656 test658 test659 test660 test661 test662 test663 \
 test664 test665 test666 test667 test668 test669 test670 test671 test672 \
 test673 test674 test675 test676 test677 test678 test679 test680 test681 \
 test682 test683 test684 test685 test686 test687 test688 test689 test690 \
-test691 test692 test693 test694 test695 test696 test697 test698 \
-\
+test691 test692 test693 test694 test695 test696 test697 test698 test699 \
 test700 test701 test702 test703 test704 test705 test706 test707 test708 \
 test709 test710 test711 test712 test713 test714 test715 test716 test717 \
 test718 test719 test720 test721 test722 test723 test724 test725 test726 \

tests/data/test699

@@ -0,0 +1,57 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+--config
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data crlf="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Last-Modified: Tue, 13 Jun 2000 12:10:00 GMT
+ETag: "21025-dc7-39462498"
+Accept-Ranges: bytes
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-head: yesyes
+
+-foo-
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+http
+</server>
+<name>
+--config with single-letter options plus one that is cleared
+</name>
+<file name="%LOGDIR/cmd">
+-Lfuhej:you
+</file>
+<command>
+http://%HOSTIP:%HTTPPORT/%TESTNUMBER -K %LOGDIR/cmd
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="yes">
+GET /%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Authorization: Basic aGVqOnlvdQ==
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>