ccanlint: check for incompatible license boilerplates within subfiles.

This checks to make sure you're not accidentally relicensing code;
eg. it's OK (though a bit impolite) to turn a BSD-licensed file into a
GPL module, but not the other way around.

tools/ccanlint/licenses.c

@@ -72,6 +72,36 @@ const struct license_info licenses[] = {
 	},
 };
 
+/* License compatibilty chart (simplified: we don't test that licenses between
+ * files are compatible). */
+bool license_compatible[LICENSE_UNKNOWN+1][LICENSE_UNKNOWN] = {
+/*       LGPL2+ LGPL2 LGPL3 LGPL  GPL2+ GPL2  GPL3  GPL   BSD   MIT   PD   */
+/* _info says: LGPL2+ */
+	{ true, false,false,true, false,false,false,false,true, true, true },
+/* _info says: LGPL2 only */
+	{ true, true, false,true, false,false,false,false,true, true, true },
+/* _info says: LGPL3 (or any later version) */
+	{ true, false,true, true, false,false,false,false,true, true, true },
+/* _info says: LGPL (no version specified) */
+	{ true, true, true, true, false,false,false,false,true, true, true },
+/* _info says: GPL2+ */
+	{ true, true, true, true, true, false,false,true, true, true, true },
+/* _info says: GPL2 only */
+	{ true, true, true, true, true, true, false,true, true, true, true },
+/* _info says: GPL3 (or any later version) */
+	{ true, true, true, true, true, false,true, true, true, true, true },
+/* _info says: GPL (unknown version) */
+	{ true, true, true, true, true, true, true, true, true, true, true },
+/* _info says: BSD (3-clause) */
+	{ false,false,false,false,false,false,false,false,true, true, true },
+/* _info says: MIT */
+	{ false,false,false,false,false,false,false,false,false,true, true },
+/* _info says: Public domain */
+	{ false,false,false,false,false,false,false,false,false,false,true },
+/* _info says something we don't understand */
+	{ false,false,false,false,false,false,false,false,false,false,true }
+};
+
 const char *get_ccan_simplified(struct ccan_file *f)
 {
 	if (!f->simplified) {

tools/ccanlint/licenses.h

@@ -26,6 +26,9 @@ struct license_info {
 	const char *clause[NUM_CLAUSES];
 };
 
+/* Is [project license][file license] compatible? */
+bool license_compatible[LICENSE_UNKNOWN+1][LICENSE_UNKNOWN];
+
 extern const struct license_info licenses[];
 
 struct ccan_file;

tools/ccanlint/tests/license_file_compat.c

+#include <tools/ccanlint/ccanlint.h>
+#include <ccan/foreach/foreach.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <limits.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <err.h>
+#include <ccan/talloc/talloc.h>
+#include <ccan/str/str.h>
+#include <ccan/str_talloc/str_talloc.h>
+
+static void check_license_file_compat(struct manifest *m,
+				      bool keep,
+				      unsigned int *timeleft,
+				      struct score *score)
+{
+	struct list_head *list;
+
+	/* FIXME: Ignore unknown licenses for now. */
+	if (m->license == LICENSE_UNKNOWN) {
+		score->pass = true;
+		score->score = score->total = 0;
+		return 0;
+	}
+
+	foreach_ptr(list, &m->c_files, &m->h_files) {
+		struct ccan_file *f;
+
+		list_for_each(list, f, list) {
+			enum license l;
+
+			/* Check they don't have boilerplate for incompatible
+			 * license! */
+			for (l = 0; l < LICENSE_UNKNOWN; l++) {
+				if (!find_boilerplate(f, l))
+					continue;
+				if (license_compatible[m->license][l])
+					break;
+				score_file_error(score, f, 0,
+						 "Found boilerplate for license '%s' which is incompatible with '%s'",
+						 licenses[l].name,
+						 licenses[m->license].name);
+				break;
+			}
+		}
+	}
+
+	if (list_empty(&score->per_file_errors)) {
+		score->pass = true;
+		score->score = score->total;
+	}
+}
+
+struct ccanlint license_file_compat = {
+	.key = "license_file_compat",
+	.name = "Source files don't contain incompatible licenses",
+	.check = check_license_file_compat,
+	.needs = "license_exists"
+};
+REGISTER_TEST(license_file_compat);