False positive warning about "too many arguments for format string"

[deivid-rodriguez]

In CRuby:

$ ruby -vwe 'sprintf("%*d", 20, 14)'
ruby 3.4.5 (2025-07-16 revision 20cda200d3) +PRISM [arm64-darwin24]

In Truffleruby:

$ ruby -vwe 'sprintf("%*d", 20, 14)'
truffleruby 24.2.1, like ruby 3.3.7, Oracle GraalVM Native [arm64-darwin20]
-e:1: warning: too many arguments for format string

[fniephaus]

Thanks for filing the ticket, @deivid-rodriguez!

[deivid-rodriguez]

This patch seems to do the trick for me, in case it helps!

diff --git a/src/main/java/org/truffleruby/core/kernel/KernelNodes.java b/src/main/java/org/truffleruby/core/kernel/KernelNodes.java
index 7a41743175..413fc44053 100644
--- a/src/main/java/org/truffleruby/core/kernel/KernelNodes.java
+++ b/src/main/java/org/truffleruby/core/kernel/KernelNodes.java
@@ -1710,6 +1710,9 @@ public abstract class KernelNodes {
                     for (var config : configs) {
                         if (!config.isLiteral()) {
                             modifiersCount++;
+                            if (config.isWidthStar() || config.isPrecisionStar()) {
+                              modifiersCount++;
+                            }
                         }
                     }
 

[fniephaus]

Thanks for the patch!