| Message ID | 20240515010805.605511-4-xandfury@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | selftests/binderfs: Fixes to binderfs_test | expand |
On Tue, May 14, 2024 at 6:08 PM Abhinav Saxena <xandfury@gmail.com> wrote: > > Change the macro argument 'fd' to '(fd)' to avoid potential precedence > issues. Without parentheses, the macro expansion could lead to > unexpected behavior when used with an expression having different > precedence levels. > > Example Code: > > #define CALC_SQR_BAD(x) (x*x) > #define CALC_SQR_GOOD(x) ((x)*(x)) > > CALC_SQR_BAD(2+3) expands to 2+(3*3)+2, giving 11 as the incorrect > answer. Enclosing with parathesis CALC_SQR_GOOD(2+3) sets the correct s/parathesis/parentheses/ > order of precedence and expands to (2+3)*(2+3), giving 25 as the > correct answer. > > Signed-off-by: Abhinav Saxena <xandfury@gmail.com> > --- > .../testing/selftests/filesystems/binderfs/binderfs_test.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > index 4a149e3d4ba4..d5dba6c1e07f 100644 > --- a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > +++ b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > @@ -30,11 +30,11 @@ > > #define close_prot_errno_disarm(fd) \ > do { \ > - if (fd >= 0) { \ > + if ((fd) >= 0) { \ > int _e_ = errno; \ > - close(fd); \ > + close((fd)); \ > errno = _e_; \ > - fd = -EBADF; \ > + (fd) = -EBADF; \ While I agree that it's generally good to add parentheses in macros, this line ensures that 'fd' must be an lvalue and not an arithmetic expression. -bw > } \ > } while (false) > > -- > 2.34.1 >
diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c index 4a149e3d4ba4..d5dba6c1e07f 100644 --- a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c +++ b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c @@ -30,11 +30,11 @@ #define close_prot_errno_disarm(fd) \ do { \ - if (fd >= 0) { \ + if ((fd) >= 0) { \ int _e_ = errno; \ - close(fd); \ + close((fd)); \ errno = _e_; \ - fd = -EBADF; \ + (fd) = -EBADF; \ } \ } while (false)
Change the macro argument 'fd' to '(fd)' to avoid potential precedence issues. Without parentheses, the macro expansion could lead to unexpected behavior when used with an expression having different precedence levels. Example Code: #define CALC_SQR_BAD(x) (x*x) #define CALC_SQR_GOOD(x) ((x)*(x)) CALC_SQR_BAD(2+3) expands to 2+(3*3)+2, giving 11 as the incorrect answer. Enclosing with parathesis CALC_SQR_GOOD(2+3) sets the correct order of precedence and expands to (2+3)*(2+3), giving 25 as the correct answer. Signed-off-by: Abhinav Saxena <xandfury@gmail.com> --- .../testing/selftests/filesystems/binderfs/binderfs_test.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) -- 2.34.1