Add printf attributes in exported headers

gcc (and other compilers) sometimes generate spurious warnings, and
thus users of public headers must be able to disable warnings.

Printf format attributes can be disabled by setting
    #define _sd_printf_attr_
before including the header file.

Also, add similar logic for sentinel attribute:
    #define _sd_sentinel_attr_
before including the header file disables the attribute.

1 files changed, 18 insertions, 6 deletions

diff --git a/src/systemd/sd-journal.h b/src/systemd/sd-journal.h
index 51653bafe9..5375d49963 100644
--- a/src/systemd/sd-journal.h
+++ b/src/systemd/sd-journal.h
@@ -34,19 +34,31 @@
 extern "C" {
 #endif
 
+#ifndef _sd_printf_attr_
+#  if __GNUC__ >= 4
+#    define _sd_printf_attr_(a,b) __attribute__ ((format (printf, a, b)))
+#  else
+#    define _sd_printf_attr_(a,b)
+#  endif
+#endif
+
+#ifndef _sd_sentinel_attr_
+#  define _sd_sentinel_attr_ __attribute__((sentinel))
+#endif
+
 /* Journal APIs. See sd-journal(3) for more information. */
 
 /* Write to daemon */
-int sd_journal_print(int priority, const char *format, ...) __attribute__ ((format (printf, 2, 3)));
-int sd_journal_printv(int priority, const char *format, va_list ap);
-int sd_journal_send(const char *format, ...) __attribute__((sentinel));
+int sd_journal_print(int priority, const char *format, ...) _sd_printf_attr_(2, 3);
+int sd_journal_printv(int priority, const char *format, va_list ap) _sd_printf_attr_(2, 0);
+int sd_journal_send(const char *format, ...) _sd_printf_attr_(1, 0) _sd_sentinel_attr_;
 int sd_journal_sendv(const struct iovec *iov, int n);
 int sd_journal_perror(const char *message);
 
 /* Used by the macros below. Don't call this directly. */
-int sd_journal_print_with_location(int priority, const char *file, const char *line, const char *func, const char *format, ...) __attribute__ ((format (printf, 5, 6)));
-int sd_journal_printv_with_location(int priority, const char *file, const char *line, const char *func, const char *format, va_list ap);
-int sd_journal_send_with_location(const char *file, const char *line, const char *func, const char *format, ...) __attribute__((sentinel));
+int sd_journal_print_with_location(int priority, const char *file, const char *line, const char *func, const char *format, ...) _sd_printf_attr_(5, 6);
+int sd_journal_printv_with_location(int priority, const char *file, const char *line, const char *func, const char *format, va_list ap) _sd_printf_attr_(5, 0);
+int sd_journal_send_with_location(const char *file, const char *line, const char *func, const char *format, ...) _sd_printf_attr_(4, 0) _sd_sentinel_attr_;
 int sd_journal_sendv_with_location(const char *file, const char *line, const char *func, const struct iovec *iov, int n);
 int sd_journal_perror_with_location(const char *file, const char *line, const char *func, const char *message);