compiler, talloc: warn if return from realloc-like functions isn't used.

[ccan] / ccan / compiler / compiler.h

diff --git a/ccan/compiler/compiler.h b/ccan/compiler/compiler.h
index be229670fd127a5f89e9e9bc6b14e4a7cc48ddce..7adcc8ca1a4ea521cb11069d3dce4dff062ecb14 100644 (file)
--- a/ccan/compiler/compiler.h
+++ b/ccan/compiler/compiler.h
@@ -10,10 +10,10 @@
  * It is usually used on logging or error routines.
  *
  * Example:
- *     void COLD_ATTRIBUTE moan(const char *reason)
- *     {
- *             fprintf(stderr, "Error: %s (%s)\n", reason, strerror(errno));
- *     }
+ * static void COLD_ATTRIBUTE moan(const char *reason)
+ * {
+ *     fprintf(stderr, "Error: %s (%s)\n", reason, strerror(errno));
+ * }
  */
 #define COLD_ATTRIBUTE __attribute__((cold))
 #else
@@ -23,13 +23,14 @@
 #if HAVE_ATTRIBUTE_PRINTF
 /**
  * PRINTF_ATTRIBUTE - a function takes printf-style arguments
- * nfmt: the 1-based number of the function's format argument.
- * narg: the 1-based number of the function's first variable argument.
+ * @nfmt: the 1-based number of the function's format argument.
+ * @narg: the 1-based number of the function's first variable argument.
  *
  * This allows the compiler to check your parameters as it does for printf().
  *
  * Example:
- *     void PRINTF_ATTRIBUTE(2,3) my_printf(char *prefix, char *format, ...);
+ * void PRINTF_ATTRIBUTE(2,3) my_printf(const char *prefix,
+ *                                     const char *fmt, ...);
  */
 #define PRINTF_ATTRIBUTE(nfmt, narg) \
        __attribute__((format(__printf__, nfmt, narg)))
@@ -58,18 +59,14 @@
  * the compiler that if it is unused it need not emit it into the source code.
  *
  * Example:
- *     // With some config options, this is unnecessary.
- *     static UNNEEDED_ATTRIBUTE int counter;
- *     ...
- *             #ifdef DEBUG
- *             counter++;
- *             #endif
- *     ...
- *     // With some config options, this is unnecessary.
- *     static UNNEEDED_ATTRIBUTE int add_to_counter(int add)
- *     {
- *             counter += add;
- *     }
+ * // With some preprocessor options, this is unnecessary.
+ * static UNNEEDED_ATTRIBUTE int counter;
+ *
+ * // With some preprocessor options, this is unnecessary.
+ * static UNNEEDED_ATTRIBUTE void add_to_counter(int add)
+ * {
+ *     counter += add;
+ * }
  */
 #define UNNEEDED_ATTRIBUTE __attribute__((unused))
 
@@ -117,7 +114,7 @@
  *     const char *greek_name(enum greek greek);
  *
  *     // Inline version.
- *     static inline _greek_name(enum greek greek)
+ *     static inline char *_greek_name(enum greek greek)
  *     {
  *             switch (greek) {
  *             case ALPHA: return "alpha";
@@ -139,4 +136,23 @@
 /* If we don't know, assume it's not. */
 #define IS_COMPILE_CONSTANT(expr) 0
 #endif
+
+#if HAVE_WARN_UNUSED_RESULT
+/**
+ * WARN_UNUSED_RESULT - warn if a function return value is unused.
+ *
+ * Used to mark a function where it is extremely unlikely that the caller
+ * can ignore the result, eg realloc().
+ *
+ * Example:
+ * // buf param may be freed by this; need return value!
+ * static char *WARN_UNUSED_RESULT enlarge(const char *buf, unsigned *size)
+ * {
+ *     return realloc(buf, (*size) *= 2);
+ * }
+ */
+#define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
+#else
+#define WARN_UNUSED_RESULT
+#endif
 #endif /* CCAN_COMPILER_H */