[cases.test_cur_int32max] and [cases.test_end_int32max] return different values for current cursor position depending on whether we use LFS_SEEK_CUR or LFS_SEEK_END (note that CUR should be equal to END, since no additional writes or seeks were performed, but returned value is different). The return value in both cases should be the same (either INT32_MAX (preferably) or 0).
[cases.test_ub_cur_int32max] and [cases.test_ub_set_int32max] work as expected (return error when seeking past LFS_FILE_MAX) but rely on undefined behaviour in lfs_file_seek (signed integer overflow), so they may not work as expected for every platform and compile options combination.
Checked on d01280e64934a09ba16cac60cf9d3a37e228bb66.
Proposed solution: compute temporary offset calculations in lfs_file_seek using int64_t before casting them to 32-bit values.
[cases.test_cur_int32max]
code = '''
lfs_t lfs;
lfs_format(&lfs, cfg) => 0;
lfs_mount(&lfs, cfg) => 0;
lfs_file_t file;
lfs_file_open(&lfs, &file, "kitty",
LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
assert(LFS_FILE_MAX == INT32_MAX);
lfs_file_seek(&lfs, &file, INT32_MAX, LFS_SEEK_SET) => INT32_MAX;
// behaviour: returns INT32_MAX, not 0 (what LFS_SEEK_END returns) /////////////////////////////
lfs_file_seek(&lfs, &file, 0, LFS_SEEK_CUR) => INT32_MAX;
lfs_file_close(&lfs, &file) => 0;
lfs_unmount(&lfs) => 0;
'''
[cases.test_end_int32max]
code = '''
lfs_t lfs;
lfs_format(&lfs, cfg) => 0;
lfs_mount(&lfs, cfg) => 0;
lfs_file_t file;
lfs_file_open(&lfs, &file, "kitty",
LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
assert(LFS_FILE_MAX == INT32_MAX);
lfs_file_seek(&lfs, &file, INT32_MAX, LFS_SEEK_SET) => INT32_MAX;
// behaviour: this returns 0, not INT32_MAX (what LFS_SEEK_CUR returns) ////////////////////////
lfs_file_seek(&lfs, &file, 0, LFS_SEEK_END) => 0;
lfs_file_close(&lfs, &file) => 0;
lfs_unmount(&lfs) => 0;
'''
[cases.test_ub_cur_int32max]
code = '''
lfs_t lfs;
lfs_format(&lfs, cfg) => 0;
lfs_mount(&lfs, cfg) => 0;
lfs_file_t file;
lfs_file_open(&lfs, &file, "kitty",
LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
assert(LFS_FILE_MAX == INT32_MAX);
lfs_file_seek(&lfs, &file, INT32_MAX, LFS_SEEK_SET) => INT32_MAX;
// ok behaviour: returns LFS_ERR_INVAL /////////////////////////////////////////////////////////
// lfs_file_seek(&lfs, &file, 10, LFS_SEEK_CUR) => 0; // [*]
lfs_file_seek(&lfs, &file, 10, LFS_SEEK_CUR) => LFS_ERR_INVAL;
// BUT, relies on UNDEFINED behaviour (signed integer overflow) on line
// if ((lfs_soff_t)file->pos + off < 0) { ... }
// when compiling with -fsanitize=undefined:
// lfs.c:3671:35: runtime error: signed integer overflow: 2147483647 + 10 cannot be represented in type 'int'
// Note, you must uncomment the line marked with [*], otherwise runtime error is not reported for some reason.
lfs_file_close(&lfs, &file) => 0;
lfs_unmount(&lfs) => 0;
'''
[cases.test_ub_set_int32max]
code = '''
lfs_t lfs;
lfs_format(&lfs, cfg) => 0;
lfs_mount(&lfs, cfg) => 0;
lfs_file_t file;
lfs_file_open(&lfs, &file, "kitty",
LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
assert(LFS_FILE_MAX == INT32_MAX);
lfs_file_seek(&lfs, &file, INT32_MAX, LFS_SEEK_SET) => INT32_MAX;
file.ctz.size = INT32_MAX; // simulate writing INT32_MAX bytes to file to force the error
lfs_file_size(&lfs, &file) => INT32_MAX;
// ok behaviour: returns LFS_ERR_INVAL /////////////////////////////////////////////////////////
// lfs_file_seek(&lfs, &file, 10, LFS_SEEK_END) => 0; // [*]
lfs_file_seek(&lfs, &file, 10, LFS_SEEK_END) => LFS_ERR_INVAL;
// BUT, relies on UNDEFINED behaviour (signed integer overflow) on line
// lfs_soff_t res = lfs_file_size_(lfs, file) + off;
// when compiling with -fsanitize=undefined:
// lfs.c:3677:20: runtime error: signed integer overflow: 2147483647 + 10 cannot be represented in type 'int'
// Note, you must uncomment the line marked with [*], otherwise runtime error is not reported for some reason.
lfs_file_close(&lfs, &file) => 0;
lfs_unmount(&lfs) => 0;
'''
Hello,
consider these 4 test cases.
Checked on d01280e64934a09ba16cac60cf9d3a37e228bb66.
Proposed solution: compute temporary offset calculations in lfs_file_seek using int64_t before casting them to 32-bit values.