On Sat, 5 Oct 2024 12:07:00 +0530 Brahmajit Das <brahmajit.xyz@xxxxxxxxx> wrote:
> show show_smap_vma_flags() has been using misspelled initializer in
> mnemonics[] - it needed to initialize 2 element array of char and it
> used NUL-padded 2 character string literals (i.e. 3-element
> initializer).
>
> This has been spotted by gcc-15[*]; prior to that gcc quietly dropped
> the 3rd eleemnt of initializers. To fix this we are increasing the size
> of mnemonics[] (from mnemonics[BITS_PER_LONG][2] to
> mnemonics[BITS_PER_LONG][3]) to accomodate the NUL-padded string
> literals.
>
> This also helps us in simplyfying the logic for printing of the flags as
> instead of printing each character from the mnemonics[], we can just
> print the mnemonics[] using seq_printf.
>
> [*]: fs/proc/task_mmu.c:917:49: error: initializer-string for array of ‘char’ is too long [-Werror=unterminate d-string-initialization]
> 917 | [0 ... (BITS_PER_LONG-1)] = "??",
> | ^~~~
> fs/proc/task_mmu.c:917:49: error: initializer-string for array of ‘char’ is too long [-Werror=unterminate d-string-initialization]
> fs/proc/task_mmu.c:917:49: error: initializer-string for array of ‘char’ is too long [-Werror=unterminate d-string-initialization]
> fs/proc/task_mmu.c:917:49: error: initializer-string for array of ‘char’ is too long [-Werror=unterminate d-string-initialization]
> fs/proc/task_mmu.c:917:49: error: initializer-string for array of ‘char’ is too long [-Werror=unterminate d-string-initialization]
> fs/proc/task_mmu.c:917:49: error: initializer-string for array of ‘char’ is too long [-Werror=unterminate d-string-initialization]
> Cc: david@xxxxxxxxxx, gorcunov@xxxxxxxxxx, linux-next@xxxxxxxxxxxxxxx, sfr@xxxxxxxxxxxxxxxx
It is strange to cc only linux-next. It isn't really a development
mailing list. Please include an appropriate development list and/or
linux-kernel on patches.
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -909,8 +909,15 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
> {
> /*
> * Don't forget to update Documentation/ on changes.
> + *
> + * The length of the second argument of mnemonics[]
> + * needs to be 3 instead of previously set 2
> + * (i.e. from [BITS_PER_LONG][2] to [BITS_PER_LONG][3])
> + * to avoid spurious
> + * -Werror=unterminated-string-initialization warning
> + * with GCC 15
> */
> - static const char mnemonics[BITS_PER_LONG][2] = {
> + static const char mnemonics[BITS_PER_LONG][3] = {
> /*
> * In case if we meet a flag we don't know about.
> */
> @@ -987,11 +994,8 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
> for (i = 0; i < BITS_PER_LONG; i++) {
> if (!mnemonics[i][0])
> continue;
> - if (vma->vm_flags & (1UL << i)) {
> - seq_putc(m, mnemonics[i][0]);
> - seq_putc(m, mnemonics[i][1]);
> - seq_putc(m, ' ');
> - }
> + if (vma->vm_flags & (1UL << i))
> + seq_printf(m, "%s ", mnemonics[i]);
> }
> seq_putc(m, '\n');
> }
Patch looks good. I'll add this to the changelog:
Stephen pointed out:
: The C standard explicitly allows for a string initializer to be too long
: due to the NUL byte at the end ... so this warning may be overzealous.
but let's make the warning go away anwyay.
