Fix a bug in stralloc_starts() and add a test.

strcalloc_starts() should have tested the return value
of `memcmp` against 0 for equality.  Fixed and added a
test case.

As an aside, one might wonder how bugs like that are
creeping into well-tested code imported from other
projects?  The answer, specific to stralloc, is that
the original code was very specific to qmail, and used
a number of additional functions specific to qmail.

Rather than import half of qmail, the version imported
into Magicka has been reworked to, instead, use
standard C functions.  The process of modifying the
code gave rise to the opportunity for bugs to creep in.
Now that a unit testing framework is in place, we can
test things in isolation more easily and hopefully
catch such things BEFORE they are published to the
master repository.

Signed-off-by: Dan Cross <patchdev@fat-dragon.org>

src/GNUmakefile.common

@@ -11,6 +11,7 @@ ODOORS:=	${DEPSDIR}/odoors/libs-${OS}/libODoors.a
 JSMN:=		${DEPSDIR}/jsmn/libjsmn.a
 CDK:=		${DEPSDIR}/cdk-5-20161210/libcdk.a
 UUID:=		${DEPSDIR}/libuuid/.libs/libuuid.a
+CUTEST:=	${DEPSDIR}/cutest-1.5/libcutest.a
 
 all:		magicka magimail magiedit ticproc mgpost magichat \
 		filecenter dosbox_shim magiftpd reset_pass
@@ -46,6 +47,9 @@ ${UUID}:
 		cd ${DEPSDIR}/libuuid/ && ./configure
 		cd ${DEPSDIR}/libuuid/ && ${MAKE} CC=${CC}
 
+${CUTEST}:
+		cd ${DEPSDIR}/cutest-1.5 && make
+
 HDRS:=		bbs.h
 OBJS:=		inih/ini.o bbs.o main.o users.o main_menu.o mail_menu.o \
 		doors.o bbs_list.o chat_system.o email.o files.o settings.o \
@@ -63,7 +67,7 @@ endif
 %.o: %.c ${HDRS}
 		${CC} -c -o $@ $< ${CFLAGS}
 
-magickawww:		${OBJS} ${WWWOBJS} ${LUA} ${ZMODEM} ${B64} ${JAMLIB} ${JSMN} ${UUID}
+magickawww:	${OBJS} ${WWWOBJS} ${LUA} ${ZMODEM} ${B64} ${JAMLIB} ${JSMN} ${UUID}
 		${CC} -o ../magicka $^ ${LIBS} -lmicrohttpd
 
 magicka:	${OBJS} ${LUA} ${ZMODEM} ${JAMLIB} ${JSMN} ${UUID}
@@ -116,3 +120,5 @@ clean:
 		cd ${UTILSDIR}/magiftpd && ${MAKE} clean
 		cd ${UTILSDIR}/reset_pass && ${MAKE} clean
 		cd ${UTILSDIR}/dosbox_shim && ${MAKE} clean
+		cd ${DEPSDIR}/libuuid && ${MAKE} clean
+		cd ${DEPSDIR}/cutest-1.5 && ${MAKE} clean

src/stralloc/stralloc.c

@@ -33,7 +33,7 @@ int stralloc_starts(stralloc *sa, const char *s) {
 	assert(sa != NULL);
 	assert(s != NULL);
 	len = strlen(s);
-	return (sa->len >= len) && memcmp(sa->s, s, len);
+	return (sa->len >= len) && memcmp(sa->s, s, len) == 0;
 }
 
 int stralloc_copyb(stralloc *sa, const char *s, size_t n) {

src/stralloc/test_stralloc.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "CuTest.h"
+
+#include "stralloc.h"
+
+void test_stralloc_starts(CuTest* tc) {
+	stralloc sa = EMPTY_STRALLOC;
+	stralloc_copys(&sa, "This is a test");
+	CuAssertTrue(tc, stralloc_starts(&sa, "This"));
+}
+
+void test_stralloc_starts_equal(CuTest* tc) {
+	stralloc sa = EMPTY_STRALLOC;
+	stralloc_copys(&sa, "This is a test");
+	CuAssertTrue(tc, stralloc_starts(&sa, "This is a test"));
+}
+
+void test_stralloc_starts_notequal(CuTest* tc) {
+	stralloc sa = EMPTY_STRALLOC;
+	stralloc_copys(&sa, "This is a test");
+	CuAssertTrue(tc, !stralloc_starts(&sa, "this"));
+}
+
+void test_stralloc_starts_toolong(CuTest* tc) {
+	stralloc sa = EMPTY_STRALLOC;
+	stralloc_copys(&sa, "This is a test");
+	CuAssertTrue(tc, !stralloc_starts(&sa, "This is a test!"));
+}
+
+CuSuite* stralloc_suite(void) {
+	CuSuite* suite = CuSuiteNew();
+
+	SUITE_ADD_TEST(suite, test_stralloc_starts);
+	SUITE_ADD_TEST(suite, test_stralloc_starts_equal);
+	SUITE_ADD_TEST(suite, test_stralloc_starts_notequal);
+	SUITE_ADD_TEST(suite, test_stralloc_starts_toolong);
+
+	return suite;
+}
+
+void RunAllTests(void) {
+	CuString *output = CuStringNew();
+	CuSuite* suite = CuSuiteNew();
+
+	CuSuiteAddSuite(suite, stralloc_suite());
+
+	CuSuiteRun(suite);
+	CuSuiteSummary(suite, output);
+	CuSuiteDetails(suite, output);
+	printf("%s\n", output->buffer);
+}
+
+int main(void) {
+	RunAllTests();
+}