在运行 Valgrind 的memcheck工具时，我经常会收到数十万条（或更多，因为 Valgrind 在 100K 时中断）小的无效读取语句，例如：
==32027== Invalid read of size 1
==32027== at 0x3AB426E26A: _IO_default_xsputn (in /lib64/libc-2.5.so)
==32027== by 0x3AB426CF70: _IO_file_xsputn@@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
这些语句指的是对我的应用程序（“ starch”）之外的函数的调用，这些函数似乎是libc. 这是我需要关心的事情吗？
编辑
如果我修改fwrite调用以删除一个字节，那么我的 gzip 流就会损坏。这是原始代码：
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;
}
编辑 2
我想我看到了问题。我有in[STARCH_Z_CHUNK]和没有in[STARCH_Z_CHUNK + 1]（同样对于out[]）。如果我通过 调整fread和fwrite语句-1，我似乎没有得到这些Invalid read of size 1语句，尽管我仍然看到很多特定于的Invalid read of size 4和：8zlib
==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
编辑 3
-g如前所述，我正在重新编译它，它确实将行号与错误相关联。
但我只是在做一个简单strncpy的argv[]变量，例如：
strncpy(uniqTag, argv[2], strlen(argv[2]) + 1);
这应该将 null 终止的argv[2]字符串复制到uniqTag，但valgrind仍将其标记为错误。
编辑 4
这是错误消息：
==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
这是两条相关的线；valgrind 说第二行是无效读取：
uniqTag = (char *)malloc(strlen(argv[2]) + 1);
strncpy(uniqTag, argv[2], strlen(argv[2]) + 1);
因为strlen(argv[2]) + 1 > strlen(argv[2])，这应该导致一个空终止的uniqTag。