diff options
Diffstat (limited to 'lib/readlink.c')
| -rw-r--r-- | lib/readlink.c | 48 |
1 files changed, 39 insertions, 9 deletions
diff --git a/lib/readlink.c b/lib/readlink.c index 4d392ef6995..531913eba3e 100644 --- a/lib/readlink.c +++ b/lib/readlink.c @@ -1,4 +1,4 @@ -/* Stub for readlink(). +/* Read the contents of a symbolic link. Copyright (C) 2003-2007, 2009-2020 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify @@ -29,7 +29,7 @@ such as DJGPP 2.03 and mingw32. */ ssize_t -readlink (const char *name, char *buf _GL_UNUSED, +readlink (char const *file, char *buf _GL_UNUSED, size_t bufsize _GL_UNUSED) { struct stat statbuf; @@ -37,7 +37,7 @@ readlink (const char *name, char *buf _GL_UNUSED, /* In general we should use lstat() here, not stat(). But on platforms without symbolic links, lstat() - if it exists - would be equivalent to stat(), therefore we can use stat(). This saves us a configure check. */ - if (stat (name, &statbuf) >= 0) + if (stat (file, &statbuf) >= 0) errno = EINVAL; return -1; } @@ -51,24 +51,54 @@ readlink (const char *name, char *buf _GL_UNUSED, for Solaris 9. */ ssize_t -rpl_readlink (const char *name, char *buf, size_t bufsize) +rpl_readlink (char const *file, char *buf, size_t bufsize) { # if READLINK_TRAILING_SLASH_BUG - size_t len = strlen (name); - if (len && name[len - 1] == '/') + size_t file_len = strlen (file); + if (file_len && file[file_len - 1] == '/') { - /* Even if name without the slash is a symlink to a directory, + /* Even if FILE without the slash is a symlink to a directory, both lstat() and stat() must resolve the trailing slash to the directory rather than the symlink. We can therefore safely use stat() to distinguish between EINVAL and ENOTDIR/ENOENT, avoiding extra overhead of rpl_lstat(). */ struct stat st; - if (stat (name, &st) == 0) + if (stat (file, &st) == 0 || errno == EOVERFLOW) errno = EINVAL; return -1; } # endif /* READLINK_TRAILING_SLASH_BUG */ - return readlink (name, buf, bufsize); + + ssize_t r = readlink (file, buf, bufsize); + +# if READLINK_TRUNCATE_BUG + if (r < 0 && errno == ERANGE) + { + /* Try again with a bigger buffer. This is just for test cases; + real code invariably discards short reads. */ + char stackbuf[4032]; + r = readlink (file, stackbuf, sizeof stackbuf); + if (r < 0) + { + if (errno == ERANGE) + { + /* Clear the buffer, which is good enough for real code. + Thankfully, no test cases try short reads of enormous + symlinks and what would be the point anyway? */ + r = bufsize; + memset (buf, 0, r); + } + } + else + { + if (bufsize < r) + r = bufsize; + memcpy (buf, stackbuf, r); + } + } +# endif + + return r; } #endif /* HAVE_READLINK */ |