ccanlint: test for C++ reserved words in headers.

Don't check the whole source, but it's nice for headers to be C++-clean.

tools/ccanlint/tests/avoids_cpp_reserved.c

+#include <tools/ccanlint/ccanlint.h>
+#include <tools/tools.h>
+#include <ccan/talloc/talloc.h>
+#include <ccan/grab_file/grab_file.h>
+#include <ccan/str/str.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 <string.h>
+#include <ctype.h>
+
+static const char *can_build(struct manifest *m)
+{
+	if (safe_mode)
+		return "Safe mode enabled";
+	return NULL;
+}
+
+static struct ccan_file *main_header(struct manifest *m)
+{
+	struct ccan_file *f;
+
+	list_for_each(&m->h_files, f, list) {
+		if (strstarts(f->name, m->basename)
+		    && strlen(f->name) == strlen(m->basename) + 2)
+			return f;
+	}
+	/* Should not happen: we depend on main_header_compiles */
+	abort();
+}
+
+static void check_headers_no_cpp(struct manifest *m,
+				 bool keep,
+				 unsigned int *timeleft, struct score *score)
+{
+	char *contents;
+	char *tmpsrc, *tmpobj, *cmdout;
+	int fd;
+	struct ccan_file *mainh = main_header(m);
+
+	tmpsrc = maybe_temp_file(m, "-included.c", keep, mainh->fullname);
+	tmpobj = maybe_temp_file(m, ".o", keep, tmpsrc);
+
+	/* We don't fail you for this. */
+	score->pass = true;
+	fd = open(tmpsrc, O_WRONLY | O_CREAT | O_EXCL, 0600);
+	if (fd < 0)
+		err(1, "Creating temporary file %s", tmpsrc);
+
+	contents = talloc_asprintf(tmpsrc,
+		   "#define class #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#define private #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#define public #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#define protected #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#define template #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#define this #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#define new #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#define delete #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#define friend #DONT_USE_CPLUSPLUS_RESERVED_NAMES\n"
+		   "#include <ccan/%s/%s.h>\n",
+				   m->basename, m->basename);
+	if (write(fd, contents, strlen(contents)) != strlen(contents))
+		err(1, "writing to temporary file %s", tmpsrc);
+	close(fd);
+
+	if (compile_object(score, tmpsrc, ccan_dir, compiler, cflags,
+			   tmpobj, &cmdout)) {
+		score->score = score->total;
+	} else {
+		score->error = talloc_asprintf(score,
+				       "Main header file with C++ names:\n%s",
+				       cmdout);
+	}
+}
+
+struct ccanlint avoids_cpp_reserved = {
+	.key = "avoids_cpp_reserved",
+	.name = "Modules main header compiles without C++ reserved words",
+	.check = check_headers_no_cpp,
+	.can_run = can_build,
+	.needs = "main_header_compiles"
+};
+
+REGISTER_TEST(avoids_cpp_reserved);