ABI compat fix for +-ve vals in amqp_error_string

To preserve ABI, map positive error codes into the negative error-code
domain in the amqp_error_string() function. This will preserve compat
with older code-bases that do amqp_error_string(-returnval)

Note: the function is marked as deprecated so the user will still get a
warning when compiling code that uses this function.

1 files changed, 10 insertions, 0 deletions

diff --git a/librabbitmq/amqp_api.c b/librabbitmq/amqp_api.c
index 8be44ad..8e037e1 100644
--- a/librabbitmq/amqp_api.c
+++ b/librabbitmq/amqp_api.c
@@ -128,6 +128,16 @@ const char *amqp_error_string2(int code)
 
 char *amqp_error_string(int code)
 {
+  /* Previously sometimes clients had to flip the sign on a return value from a
+   * function to get the correct error code. Now, all error codes are negative.
+   * To keep people's legacy code running correctly, we map all error codes to
+   * negative values.
+   *
+   * This is only done with this deprecated function.
+   */
+  if (code > 0) {
+    code = -code;
+  }
   return strdup(amqp_error_string2(code));
 }