the log wrapper in C/C++ accepts formats

pam-module/include/rust_backend_logging_c.h

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: Apache-2.0
+// C printf-style wrappers for Rust logging FFI
+
+#pragma once
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include "rust_backend_ffi.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Buffer size for formatted messages. Documented truncation behavior.
+#define RUST_LOG_FMT_BUFSZ 2048
+
+static inline void rust_log_vprintf_level(RustLogLevel level, const char* fmt, va_list ap) {
+    if (fmt == NULL) {
+        rust_log_event_with_level("(null format)", level);
+        return;
+    }
+    char buf[RUST_LOG_FMT_BUFSZ];
+    int ret = vsnprintf(buf, RUST_LOG_FMT_BUFSZ, fmt, ap);
+    if (ret < 0) {
+        rust_log_event_with_level("(format error)", level);
+        return;
+    }
+    // vsnprintf guarantees NUL-termination as long as size>0
+    buf[RUST_LOG_FMT_BUFSZ - 1] = '\0';
+    rust_log_event_with_level(buf, level);
+}
+
+static inline void rust_log_printf_level(RustLogLevel level, const char* fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    rust_log_vprintf_level(level, fmt, ap);
+    va_end(ap);
+}
+
+// Convenience per-level functions
+static inline void rust_logf_fatal(const char* fmt, ...) {
+    va_list ap; va_start(ap, fmt); rust_log_vprintf_level(RUST_LOG_LEVEL_FATAL, fmt, ap); va_end(ap);
+}
+static inline void rust_logf_error(const char* fmt, ...) {
+    va_list ap; va_start(ap, fmt); rust_log_vprintf_level(RUST_LOG_LEVEL_ERROR, fmt, ap); va_end(ap);
+}
+static inline void rust_logf_warn(const char* fmt, ...) {
+    va_list ap; va_start(ap, fmt); rust_log_vprintf_level(RUST_LOG_LEVEL_WARN, fmt, ap); va_end(ap);
+}
+static inline void rust_logf_info(const char* fmt, ...) {
+    va_list ap; va_start(ap, fmt); rust_log_vprintf_level(RUST_LOG_LEVEL_INFO, fmt, ap); va_end(ap);
+}
+static inline void rust_logf_debug(const char* fmt, ...) {
+    va_list ap; va_start(ap, fmt); rust_log_vprintf_level(RUST_LOG_LEVEL_DEBUG, fmt, ap); va_end(ap);
+}
+static inline void rust_logf_trace(const char* fmt, ...) {
+    va_list ap; va_start(ap, fmt); rust_log_vprintf_level(RUST_LOG_LEVEL_TRACE, fmt, ap); va_end(ap);
+}
+
+// Convenience macros for C/C++ callers (variadic macro)
+// Support both C99 and C++ compilers that support variadic macros
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) || defined(__cplusplus)
+  #define RUST_LOGF_FATAL(fmt, ...) rust_log_printf_level(RUST_LOG_LEVEL_FATAL, (fmt), ##__VA_ARGS__)
+  #define RUST_LOGF_ERROR(fmt, ...) rust_log_printf_level(RUST_LOG_LEVEL_ERROR, (fmt), ##__VA_ARGS__)
+  #define RUST_LOGF_WARN(fmt, ...)  rust_log_printf_level(RUST_LOG_LEVEL_WARN,  (fmt), ##__VA_ARGS__)
+  #define RUST_LOGF_INFO(fmt, ...)  rust_log_printf_level(RUST_LOG_LEVEL_INFO,  (fmt), ##__VA_ARGS__)
+  #define RUST_LOGF_DEBUG(fmt, ...) rust_log_printf_level(RUST_LOG_LEVEL_DEBUG, (fmt), ##__VA_ARGS__)
+  #define RUST_LOGF_TRACE(fmt, ...) rust_log_printf_level(RUST_LOG_LEVEL_TRACE, (fmt), ##__VA_ARGS__)
+#endif
+
+#ifdef __cplusplus
+}
+#endif