Allow Empty Format Strings in Error Macro Invocations

`-Wall` implies `-Wformat-zero-length`, which will cause compilation to fail
under `-Werror` when an empty string is passed as the format string to a
`printf`-family function. This commit moves us back to prefixing the provided
format string, which successfully avoids that warning.

However, this removes the failure mode where that `RAWLOG` invocation would
fail to compile when no format string was provided at all (which was desirable
to avoid having code that would successfully compile normally but fail under
`-pedantic`, which *does* require that a non-zero number of args are provided).

So this commit also introduces a function which does nothing at all, but will
fail to compile if not provided with at least one argument, which is a string.
This successfully links the compilability of pedantic and non-pedantic builds.

diff --git a/lib/common/zstd_internal.h b/lib/common/zstd_internal.h
index 05225e32e243f7e9073a5a04ae3fc60436ff70f8..856ee14873acc0028a4558dd681f8af66b82ce1f 100644 (file)
--- a/lib/common/zstd_internal.h
+++ b/lib/common/zstd_internal.h
@@ -53,6 +53,10 @@ extern "C" {
 #define MIN(a,b) ((a)<(b) ? (a) : (b))
 #define MAX(a,b) ((a)>(b) ? (a) : (b))
 
+static INLINE_KEYWORD UNUSED_ATTR void _force_has_formatting_string(const char *format, ...) {
+  (void)format;
+}
+
 /**
  * Return the specified error if the condition evaluates to true.
  *
@@ -62,8 +66,10 @@ extern "C" {
  */
 #define RETURN_ERROR_IF(cond, err, ...) \
   if (cond) { \
-    RAWLOG(3, "%s:%d: ERROR!: check %s failed, returning %s: ", __FILE__, __LINE__, ZSTD_QUOTE(cond), ZSTD_QUOTE(ERROR(err))); \
-    RAWLOG(3, __VA_ARGS__); \
+    RAWLOG(3, "%s:%d: ERROR!: check %s failed, returning %s", \
+           __FILE__, __LINE__, ZSTD_QUOTE(cond), ZSTD_QUOTE(ERROR(err))); \
+    _force_has_formatting_string(__VA_ARGS__); \
+    RAWLOG(3, ": " __VA_ARGS__); \
     RAWLOG(3, "\n"); \
     return ERROR(err); \
   }
@@ -75,8 +81,10 @@ extern "C" {
  */
 #define RETURN_ERROR(err, ...) \
   do { \
-    RAWLOG(3, "%s:%d: ERROR!: unconditional check failed, returning %s: ", __FILE__, __LINE__, ZSTD_QUOTE(ERROR(err))); \
-    RAWLOG(3, __VA_ARGS__); \
+    RAWLOG(3, "%s:%d: ERROR!: unconditional check failed, returning %s", \
+           __FILE__, __LINE__, ZSTD_QUOTE(ERROR(err))); \
+    _force_has_formatting_string(__VA_ARGS__); \
+    RAWLOG(3, ": " __VA_ARGS__); \
     RAWLOG(3, "\n"); \
     return ERROR(err); \
   } while(0);
@@ -90,8 +98,10 @@ extern "C" {
   do { \
     size_t const err_code = (err); \
     if (ERR_isError(err_code)) { \
-      RAWLOG(3, "%s:%d: ERROR!: forwarding error in %s: %s: ", __FILE__, __LINE__, ZSTD_QUOTE(err), ERR_getErrorName(err_code)); \
-      RAWLOG(3, __VA_ARGS__); \
+      RAWLOG(3, "%s:%d: ERROR!: forwarding error in %s: %s", \
+             __FILE__, __LINE__, ZSTD_QUOTE(err), ERR_getErrorName(err_code)); \
+      _force_has_formatting_string(__VA_ARGS__); \
+      RAWLOG(3, ": " __VA_ARGS__); \
       RAWLOG(3, "\n"); \
       return err_code; \
     } \