From 4e5b57095bee4cd50e2095ad7043f5a885c2c180 Mon Sep 17 00:00:00 2001
From: jvoisin
Date: Fri, 14 Nov 2025 15:06:23 +0100
Subject: Add `format` annotations

---
 include/fortify-headers.h | 11 +++++++++++
 include/stdio.h           |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/include/fortify-headers.h b/include/fortify-headers.h
index a9b7498..deff351 100644
--- a/include/fortify-headers.h
+++ b/include/fortify-headers.h
@@ -70,4 +70,15 @@
 #define __access(...)
 #endif
 
+/* This needs to be two different conditions: https://gcc.gnu.org/onlinedocs/cpp/_005f_005fhas_005fattribute.html */
+#if defined __has_attribute
+#if __has_attribute (format)
+#define __format(...) __attribute__ ((format (__VA_ARGS__)))
+#else
+#define __format(...)
+#endif
+#else
+#define __format(...)
+#endif
+
 #endif
diff --git a/include/stdio.h b/include/stdio.h
index 67738ed..52032ae 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -121,6 +121,7 @@ _FORTIFY_FN(vsprintf) int vsprintf(char * _FORTIFY_POS0 __s, const char *__f,
  * 3) not implementing these under clang, which is what we do for now
  */
 
+__format(printf, 3, 4)
 _FORTIFY_FN(snprintf) int snprintf(char *__s, size_t __n,
                                     const char *__f, ...)
 {
@@ -131,6 +132,7 @@ _FORTIFY_FN(snprintf) int snprintf(char *__s, size_t __n,
 	return __orig_snprintf(__s, __n, __f, __builtin_va_arg_pack());
 }
 
+__format(printf, 2, 3)
 _FORTIFY_FN(sprintf) int sprintf(char *__s, const char *__f, ...)
 {
 	size_t __b = __bos(__s, 0);
-- 
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