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    SubjectRe: linux-next: driver-core tree build failure
    On Tue, 10 Mar 2009, Stephen Rothwell wrote:
    > Today's linux-next build (x86_64 allmodconfig) failed like this:
    >
    > crypto/zlib.c: In function 'zlib_compress_update':
    > crypto/zlib.c:148: warning: initialization makes integer from pointer without a cast
    > crypto/zlib.c:148: error: initializer element is not computable at load time
    > crypto/zlib.c:148: error: (near initialization for 'descriptor.primary_hash')
    > crypto/zlib.c:148: warning: excess elements in struct initializer
    > crypto/zlib.c:148: warning: (near initialization for 'descriptor')
    >
    > And many more similar. This line is a pr_debug() statement, so the
    > finger points at commit 25b67b75587d43ff3f09ad88c03c70a38372d95d
    > ("dynamic debug: combine dprintk and dynamic printk") from the
    > driver-core tree.
    >
    > The preprocessed code looks like this:
    >
    > static int zlib_compress_update(struct crypto_pcomp *tfm,
    > struct comp_request *req)
    > {
    > int ret;
    > struct zlib_ctx *dctx = crypto_tfm_ctx(crypto_pcomp_tfm(tfm));
    > struct z_stream_s *stream = &dctx->comp_stream;
    >
    > do { do { static struct _ddebug descriptor __attribute__((__used__)) __attribute__((section("__verbose"), aligned(8))) = { "zlib", __func__, "/scratch/sfr/next/crypto/zlib.c", "%s: " "avail_in %u, avail_out %u\n", __func__, 55, 33, 148, 0 }; if (({ int __ret = 0; if (__builtin_expect(!!((dynamic_debug_enabled & (1LL << 55)) && (dynamic_debug_enabled2 & (1LL << 33))), 0)) if (__builtin_expect(!!(descriptor.flags), 0)) __ret = 1; __ret; })) printk("<7>" "zlib" ":" "%s: " "avail_in %u, avail_out %u\n", __func__, req->avail_in, req->avail_out); } while (0); } while (0);
    >
    > The problem is the line:
    >
    > #define pr_fmt(fmt) "%s: " fmt, __func__
    >
    > in crypto/zlib.c which was introduced by commit
    > bf68e65ec9ea61e32ab71bef59aa5d24d255241f ("crypto: zlib - New zlib crypto
    > module, using pcomp") from the crypto tree.
    >
    > For today, I have removed the above line from crypto/zlib.c, but
    > something better needs to be done for tomorrow!

    I had a closer look. It happens on all archs, if CONFIG_DYNAMIC_DEBUG=y.

    crypto/zlib.c has:

    #define pr_fmt(fmt) "%s: " fmt, __func__

    If CONFIG_DYNAMIC_DEBUG is set, include/linux/kernel.h has:

    #define pr_debug(fmt, ...) do { \
    dynamic_pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \
    } while (0)

    include/linux/dynamic_debug.h has:

    #define dynamic_pr_debug(fmt, ...) do { \
    static struct _ddebug descriptor \
    __used \
    __attribute__((section("__verbose"), aligned(8))) = \
    { KBUILD_MODNAME, __func__, __FILE__, fmt, DEBUG_HASH, \
    DEBUG_HASH2, __LINE__, _DPRINTK_FLAGS_DEFAULT }; \
    if (__dynamic_dbg_enabled(descriptor)) \
    printk(KERN_DEBUG KBUILD_MODNAME ":" fmt, \
    ##__VA_ARGS__); \
    } while (0)


    So in crypto/zlib.c,

    | pr_debug("avail_in %u, avail_out %u\n", req->avail_in, req->avail_out);

    is expanded to

    | do {
    | do {
    | static struct _ddebug descriptor
    | __attribute__((__used__))
    | __attribute__((section("__verbose"), aligned(8))) = {
    | "zlib",
    | __func__,
    | "crypto/zlib.c",
    | "%s: " "avail_in %u, avail_out %u\n",
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    This is the actual format string

    | __func__,
    ^^^^^^^^^
    But this is the first parameter, which should not be here!!!

    | 55,
    | 33,
    | 150,
    | 0
    | };
    | if (({
    | int __ret = 0;
    | if (__builtin_expect(!!((dynamic_debug_enabled & (1LL << 55)) &&
    | (dynamic_debug_enabled2 & (1LL << 33))), 0))
    | if (__builtin_expect(!!(descriptor.flags), 0))
    | __ret = 1;
    | __ret;
    | }))
    | printk("<7>" "zlib" ":" "%s: " "avail_in %u, avail_out %u\n", __func__,
    | req->avail_in, req->avail_out);
    | } while (0);
    | } while (0);

    Due the the superfluous `__func__', all field members are shifted by one
    position, and compilation breaks.

    Apparently inside dynamic_pr_debug(), `fmt' is:

    "avail_in %u, avail_out %u\n", __func__

    instead of only the part before the comma:

    "avail_in %u, avail_out %u\n"


    For the non-CONFIG_DYNAMIC_DEBUG case, pr_debug() is expanded correctly:

    DEBUG is defined:

    #define pr_debug(fmt, ...) \
    printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)

    and the line is expanded to:

    | printk("<7>" "%s: " "avail_in %u, avail_out %u\n", __func__, req->avail_in, req->avail_out);

    DEBUG is not defined:

    #define pr_debug(fmt, ...) \
    ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; })

    and the line is expanded to:

    | ({ if (0) printk("<7>" "%s: " "avail_in %u, avail_out %u\n", __func__, req->avail_in, req->avail_out); 0; });

    Why doesn't it work for dynamic_pr_debug()?

    BTW, Martin: Is `#define pr_fmt(fmt) "%s: " fmt, __func__' a valid and
    intended usage of your pr_fmt() infrastructure?

    Thanks!

    With kind regards,

    Geert Uytterhoeven
    Software Architect

    Sony Techsoft Centre Europe
    The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

    Phone: +32 (0)2 700 8453
    Fax: +32 (0)2 700 8622
    E-mail: Geert.Uytterhoeven@sonycom.com
    Internet: http://www.sony-europe.com/

    A division of Sony Europe (Belgium) N.V.
    VAT BE 0413.825.160 · RPR Brussels
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