[Libguestfs] [libnbd PATCH v5 4/5] vector: introduce DEFINE_POINTER_VECTOR_TYPE()

The "name##_iter" function is used 11 times in libnbd; in all those cases, "name" is "string_vector", and the "f" callback is "free": string_vector_iter (..., (void *) free); Casting "free" to (void*) is ugly. (Well-defined by POSIX, but still.) Furthermore, in all 11 cases, the freeing of the vector's strings is immediately followed by the release of the vector's array-of-pointers too. (This additional step is not expressed consistently across libnbd: it's sometimes spelled as free(vec.ptr), sometimes as string_vector_reset(&vec).) Introduce "name##_empty", which performs both steps at the same time. Keep the generic "name##_iter" function definition, as we'll want to synch this patch to nbdkit, and in nbdkit, "name##_iter" has other uses as well. Expose the "name##_empty" function definition with a new, separate macro: ADD_VECTOR_EMPTY_METHOD(). The existent DEFINE_VECTOR_TYPE() macro permits such element types that are not pointers, or are pointers to const- and/or volatile-qualified objects. Whereas "name##_empty" requires that the elements be pointers to dynamically allocated, non-const, non-volatile objects. Add DEFINE_POINTER_VECTOR_TYPE() that expands to both DEFINE_VECTOR_TYPE() and the additive ADD_VECTOR_EMPTY_METHOD(). ( For example, after typedef char foobar[5]; the following compiles (as expected): DEFINE_VECTOR_TYPE (foobar_vector, foobar); and the following fails to build (as expected): DEFINE_POINTER_VECTOR_TYPE (foobar_vector_bad, foobar); with the diagnostics including ) Switch "string_vector" to DEFINE_POINTER_VECTOR_TYPE(). The 11 string_vector_iter() call sites continue working; they will be converted to string_vector_empty() in a subsequent patch. Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; --- Notes: v5: - resolve conflict from update to previous patch - force semicolon after ADD_VECTOR_EMPTY_METHOD() and DEFINE_POINTER_VECTOR_TYPE() too - update example macro invocations in the commit message v4: - rename DEFINE_VECTOR_EMPTY to ADD_VECTOR_EMPTY_METHOD - introduce DEFINE_POINTER_VECTOR_TYPE as a convenience macro for DEFINE_VECTOR_TYPE plus ADD_VECTOR_EMPTY_METHOD - keep "name##_iter" - statically assert in "name##_empty" that the vector contains pointers - redefine string_vector with DEFINE_POINTER_VECTOR_TYPE now, rather than augmenting it as DEFINE_VECTOR_TYPE + (pre-rename, additive) DEFINE_VECTOR_EMPTY - split the call site conversions to a separate patch common/utils/string-vector.h | 2 +- common/utils/vector.h | 35 ++++++++++++++++++++ 2 files changed, 36 insertions(+), 1 deletion(-) diff --git a/common/utils/string-vector.h b/common/utils/string-vector.h index aa33fd48ceb5..115d7d484c71 100644 --- a/common/utils/string-vector.h +++ b/common/utils/string-vector.h @@ -37,6 +37,6 @@ #include "vector.h" -DEFINE_VECTOR_TYPE (string_vector, char *); +DEFINE_POINTER_VECTOR_TYPE (string_vector, char *); #endif /* STRING_VECTOR_H */ diff --git a/common/utils/vector.h b/common/utils/vector.h index b9b88ba02e7d..bdba02f7ebee 100644 --- a/common/utils/vector.h +++ b/common/utils/vector.h @@ -44,6 +44,9 @@ #include <assert.h> #include <string.h> +#include "compiler-macros.h" +#include "static-assert.h" + #ifdef __clang__ #pragma clang diagnostic ignored "-Wunused-function" #pragma clang diagnostic ignored "-Wduplicate-decl-specifier" @@ -183,6 +186,38 @@ #define empty_vector { .ptr = NULL, .len = 0, .cap = 0 } +/* This macro should only be used if: + * - the vector contains pointers, and + * - the pointed-to objects are: + * - neither const- nor volatile-qualified, and + * - allocated with malloc() or equivalent. + */ +#define ADD_VECTOR_EMPTY_METHOD(name) \ + /* Call free() on each element of the vector, then reset the vector. \ + */ \ + static inline void __attribute__ ((__unused__)) \ + name##_empty (name *v) \ + { \ + size_t i; \ + for (i = 0; i < v->len; ++i) { \ + STATIC_ASSERT (TYPE_IS_POINTER (v->ptr[i]), \ + _vector_contains_pointers); \ + free (v->ptr[i]); \ + } \ + name##_reset (v); \ + } \ + \ + /* Force callers to supply ';'. */ \ + struct name + +/* Convenience macro tying together DEFINE_VECTOR_TYPE() and + * ADD_VECTOR_EMPTY_METHOD(). Inherit and forward the requirement for a + * trailing semicolon from ADD_VECTOR_EMPTY_METHOD() to the caller. + */ +#define DEFINE_POINTER_VECTOR_TYPE(name, type) \ + DEFINE_VECTOR_TYPE (name, type); \ + ADD_VECTOR_EMPTY_METHOD (name) + struct generic_vector { void *ptr; size_t len;