Re: [Xen-devel] [PATCH 14/19] libxl: Get compiler to warn about gc_opt==NULL

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-06-08 at 18:34 +0100, Ian Jackson wrote:
> Since it used to be legal to pass gc_opt==NULL, and there are various
> patches floating about and under developmetn which do so, add a

                                   development

> compiler annotation which makes the build fail when that is done.
> 
> This turns a runtime crash into a build failure, and should ensure
> that we don't accidentally commit a broken combination of patches.
> 
> This is something of an annoying approach because it adds a macro
> invocation to the RHS of every declaration of a function taking a
> gc_opt.  So it should be reverted after Xen 4.2rc1.

This patch will itself break the build until a subsequent patch, won't
it? Shuffle it afterwards?

> Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

Wherever it ends up in the sequence:
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> ---
>  tools/libxl/libxl_internal.h |   21 +++++++++++++--------
>  1 files changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index e69482c..8635764 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -453,28 +453,33 @@ static inline libxl_ctx *libxl__gc_owner(libxl__gc *gc)
>   * psuedo-gc.
>   */
>  /* register ptr in gc for free on exit from outermost libxl callframe. */
> -_hidden void libxl__ptr_add(libxl__gc *gc_opt, void *ptr /* may be NULL */);
> +
> +#define NN1 __attribute__((nonnull(1)))
> + /* It used to be legal to pass NULL for gc_opt.  Get the compiler to
> +  * warn about this if any slip through. */
> +
> +_hidden void libxl__ptr_add(libxl__gc *gc_opt, void *ptr /* may be NULL */) 
> NN1;
>  /* if this is the outermost libxl callframe then free all pointers in @gc */
>  _hidden void libxl__free_all(libxl__gc *gc);
>  /* allocate and zero @bytes. (similar to a gc'd malloc(3)+memzero()) */
> -_hidden void *libxl__zalloc(libxl__gc *gc_opt, int bytes);
> +_hidden void *libxl__zalloc(libxl__gc *gc_opt, int bytes) NN1;
>  /* allocate and zero memory for an array of @nmemb members of @size each.
>   * (similar to a gc'd calloc(3)). */
> -_hidden void *libxl__calloc(libxl__gc *gc_opt, size_t nmemb, size_t size);
> +_hidden void *libxl__calloc(libxl__gc *gc_opt, size_t nmemb, size_t size) 
> NN1;
>  /* change the size of the memory block pointed to by @ptr to @new_size bytes.
>   * unlike other allocation functions here any additional space between the
>   * oldsize and @new_size is not initialised (similar to a gc'd realloc(3)). 
> */
> -_hidden void *libxl__realloc(libxl__gc *gc_opt, void *ptr, size_t new_size);
> +_hidden void *libxl__realloc(libxl__gc *gc_opt, void *ptr, size_t new_size) 
> NN1;
>  /* print @fmt into an allocated string large enoughto contain the result.
>   * (similar to gc'd asprintf(3)). */
> -_hidden char *libxl__sprintf(libxl__gc *gc_opt, const char *fmt, ...) 
> PRINTF_ATTRIBUTE(2, 3);
> +_hidden char *libxl__sprintf(libxl__gc *gc_opt, const char *fmt, ...) 
> PRINTF_ATTRIBUTE(2, 3) NN1;
>  /* duplicate the string @c (similar to a gc'd strdup(3)). */
> -_hidden char *libxl__strdup(libxl__gc *gc_opt, const char *c);
> +_hidden char *libxl__strdup(libxl__gc *gc_opt, const char *c) NN1;
>  /* duplicate at most @n bytes of string @c (similar to a gc'd strndup(3)). */
> -_hidden char *libxl__strndup(libxl__gc *gc_opt, const char *c, size_t n);
> +_hidden char *libxl__strndup(libxl__gc *gc_opt, const char *c, size_t n) NN1;
>  /* strip the last path component from @s and return as a newly allocated
>   * string. (similar to a gc'd dirname(3)). */
> -_hidden char *libxl__dirname(libxl__gc *gc_opt, const char *s);
> +_hidden char *libxl__dirname(libxl__gc *gc_opt, const char *s) NN1;
>  
>  /* Each of these logs errors and returns a libxl error code.
>   * They do not mind if path is already removed.



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