當運行Valgrind的的memcheck
工具,我經常收到幾十萬(或更多,因爲Valgrind的在100K切斷)的小無效讀語句,如:我是否需要擔心Valgrind在我的應用程序範圍之外報告錯誤?
==32027== Invalid read of size 1
==32027== at 0x3AB426E26A: _IO_default_xsputn (in /lib64/libc-2.5.so)
==32027== by 0x3AB426CF70: [email protected]@GLIBC_2.2.5 (in /lib64/libc-2.5.so)
==32027== by 0x3AB42621FA: fwrite (in /lib64/libc-2.5.so)
==32027== by 0x4018CA: STARCH_gzip_deflate (in /home/areynolds/trunk/utility/applications/bed/starch/bin/starch)
==32027== by 0x401F48: compressFileWithGzip (in /home/areynolds/trunk/utility/applications/bed/starch/bin/starch)
==32027== by 0x4028B5: transformInput (in /home/areynolds/trunk/utility/applications/bed/starch/bin/starch)
==32027== by 0x402F12: main (in /home/areynolds/trunk/utility/applications/bed/starch/bin/starch)
==32027== Address 0x7febb9b3c is on thread 1's stack
這些陳述是指函數調用外我的申請(「starch
」)和似乎是libc
的一部分。這是我需要關心的嗎?
編輯
如果我修改fwrite
調用刪除一個字節,然後我的gzip流被破壞。這裏是原代碼:
int STARCH_gzip_deflate(FILE *source, FILE *dest, int level) {
int ret, flush;
unsigned have;
z_stream strm;
unsigned char in[STARCH_Z_CHUNK];
unsigned char out[STARCH_Z_CHUNK];
/* initialize deflate state */
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
/* deflateInit2 allows creation of archive with gzip header, i.e. a gzip file */
/* cf. http://www.zlib.net/manual.html */
ret = deflateInit2(&strm, level, Z_DEFLATED, (15+16), 8, Z_DEFAULT_STRATEGY);
if (ret != Z_OK)
return ret;
/* compress until end of file */
do {
strm.avail_in = fread(in, 1, STARCH_Z_CHUNK, source);
if (ferror(source)) {
(void)deflateEnd(&strm);
return Z_ERRNO;
}
flush = feof(source) ? Z_FINISH : Z_NO_FLUSH;
strm.next_in = in;
do {
strm.avail_out = STARCH_Z_CHUNK;
strm.next_out = out;
ret = deflate(&strm, flush);
assert(ret != Z_STREAM_ERROR);
have = STARCH_Z_CHUNK - strm.avail_out;
/* invalid read happens here */
if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
(void)deflateEnd(&strm);
return Z_ERRNO;
}
} while (strm.avail_out == 0);
assert(strm.avail_in == 0);
} while (flush != Z_FINISH);
assert(ret == Z_STREAM_END);
/* clean up and return */
(void)deflateEnd(&strm);
return Z_OK;
}
EDIT 2
我想我看到的問題。我有in[STARCH_Z_CHUNK]
而不是in[STARCH_Z_CHUNK + 1]
(同樣對於out[]
)。如果我通過-1
同時調整fread
和fwrite
聲明,我似乎並沒有得到那些Invalid read of size 1
陳述,儘管我仍然看到了大量的Invalid read of size 4
和8
所特有的zlib
:
==32624== Invalid read of size 4
==32624== at 0x3AB5206455: deflateInit2_ (in /usr/lib64/libz.so.1.2.3)
==32624== by 0x40180E: STARCH_gzip_deflate (in /home/areynolds/trunk/utility/applications/bed/starch/bin/starch)
==32624== by 0x401F48: compressFileWithGzip (in /home/areynolds/trunk/utility/applications/bed/starch/bin/starch)
==32624== by 0x402C03: transformInput (in /home/areynolds/trunk/utility/applications/bed/starch/bin/starch)
==32624== by 0x402F12: main (in /home/areynolds/trunk/utility/applications/bed/starch/bin/starch)
==32624== Address 0x7feafde38 is on thread 1's stack
編輯3
我正在用-g
重新編譯,如前所述,它將行號與錯誤關聯起來。
但我只是在做argv[]
的strncpy
一個簡單的變量,例如:
strncpy(uniqTag, argv[2], strlen(argv[2]) + 1);
這應在空值終止字符串argv[2]
複製到uniqTag
,但仍valgrind
標誌着這是一個錯誤。
EDIT 4
這裏的錯誤消息:
==3682== Invalid read of size 1
==3682== at 0x4A081C1: strncpy (mc_replace_strmem.c:329)
==3682== by 0x4022F1: parseCommandLineInputs (starch.c:589)
==3682== by 0x402F20: main (starch.c:46)
==3682== Address 0x7fedffe11 is on thread 1's stac
下面是兩個相關線; Valgrind是說,第二行是無效讀:
uniqTag = (char *)malloc(strlen(argv[2]) + 1);
strncpy(uniqTag, argv[2], strlen(argv[2]) + 1);
因爲strlen(argv[2]) + 1 > strlen(argv[2])
,這將導致一個空值終止uniqTag
。
其實它可能是你的緩衝區,需要得到大一點,而不是fwrite(),需要剋制自己... – thkala 2010-11-16 22:09:27
嘗試增加緩衝區的大小1,看看會發生什麼 – thkala 2010-11-16 22:19:18
順便說一句,你是用調試符號編譯你的代碼?如果在編譯器選項中使用-g(假設你使用gcc),valgrind會發出更精確和有用的消息。 – thkala 2010-11-16 22:21:01