curl/lib/content_encoding.h
Patrick Monnerat 4399b0303a
content_encoding: use writer struct subclasses for different encodings
The variable-sized encoding-specific storage of a struct contenc_writer
currently relies on void * alignment that may be insufficient with
regards to the specific storage fields, although having not caused any
problems yet.

In addition, gcc 11.3 issues a warning on access to fields of partially
allocated structures that can occur when the specific storage size is 0:

  content_encoding.c: In function ‘Curl_build_unencoding_stack’:
  content_encoding.c:980:21: warning: array subscript ‘struct contenc_writer[0]’ is partly outside array bounds of ‘unsigned char[16]’ [-Warray-bounds]
    980 |     writer->handler = handler;
        |     ~~~~~~~~~~~~~~~~^~~~~~~~~
  In file included from content_encoding.c:49:
  memdebug.h:115:29: note: referencing an object of size 16 allocated by ‘curl_dbg_calloc’
    115 | #define calloc(nbelem,size) curl_dbg_calloc(nbelem, size, __LINE__, __FILE__)
        |                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  content_encoding.c:977:60: note: in expansion of macro ‘calloc’
    977 |   struct contenc_writer *writer = (struct contenc_writer *)calloc(1, sz);

To solve both these problems, the current commit replaces the
contenc_writer/params structure pairs by "subclasses" of struct
contenc_writer. These are structures that contain a contenc_writer at
offset 0. Proper field alignment is therefore handled by the compiler and
full structure allocation is performed, silencing the warnings.

Closes #9455
2022-09-11 14:46:52 +02:00

57 lines
2.3 KiB
C

#ifndef HEADER_CURL_CONTENT_ENCODING_H
#define HEADER_CURL_CONTENT_ENCODING_H
/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
* SPDX-License-Identifier: curl
*
***************************************************************************/
#include "curl_setup.h"
struct contenc_writer {
const struct content_encoding *handler; /* Encoding handler. */
struct contenc_writer *downstream; /* Downstream writer. */
};
/* Content encoding writer. */
struct content_encoding {
const char *name; /* Encoding name. */
const char *alias; /* Encoding name alias. */
CURLcode (*init_writer)(struct Curl_easy *data,
struct contenc_writer *writer);
CURLcode (*unencode_write)(struct Curl_easy *data,
struct contenc_writer *writer,
const char *buf, size_t nbytes);
void (*close_writer)(struct Curl_easy *data,
struct contenc_writer *writer);
size_t writersize;
};
CURLcode Curl_build_unencoding_stack(struct Curl_easy *data,
const char *enclist, int maybechunked);
CURLcode Curl_unencode_write(struct Curl_easy *data,
struct contenc_writer *writer,
const char *buf, size_t nbytes);
void Curl_unencode_cleanup(struct Curl_easy *data);
char *Curl_all_content_encodings(void);
#endif /* HEADER_CURL_CONTENT_ENCODING_H */