BUG: errors: remove printf positional args for user messages context

Change the algorithm for the generation of the user messages context
prefix. Remove the dubious API relying on optional printf positional
arguments. This may be non portable, and in fact the CI glibc crashes
with the following error when some arguments are not present in the
format string :

"invalid %N$ use detected".

Now, a fixed buffer attached to the context instance is allocated once
for the program lifetime. Then call repeatedly snprintf with the
optional arguments of context if present to build the context string.
The buffer is deallocated via a per-thread free handler.

This does not need to be backported.

1 files changed, 4 insertions, 0 deletions

diff --git a/include/haproxy/errors.h b/include/haproxy/errors.h
index 6dd60f1e1..a6c117714 100644
--- a/include/haproxy/errors.h
+++ b/include/haproxy/errors.h
@@ -25,6 +25,8 @@
 #include <stdarg.h>
 #include <stdio.h>
 
+#include <haproxy/buf-t.h>
+
 /* These flags may be used in various functions which are called from within
  * loops (eg: to start all listeners from all proxies). They provide enough
  * information to let the caller decide what to do. ERR_WARN and ERR_ALERT
@@ -67,6 +69,8 @@ const char *usermsgs_str(void);
 /************ Error reporting functions ***********/
 
 struct usermsgs_ctx {
+	struct buffer str;
+
 	const char *prefix;  /* prefix of every output */
 	const char *file;    /* related filename for config parsing */
 	int line;            /* related line number for config parsing */