Re: [PATCH kmod 09/13] libkmod: swap alloca usage for a few assert_cc

[Emil Velikov <emil.l.velikov@gmail.com>]

On Tue, 30 Apr 2024 at 19:43, Lucas De Marchi <lucas.demarchi@intel.com> wrote:
>
> On Tue, Apr 30, 2024 at 07:27:00PM GMT, Emil Velikov wrote:
> >On Tue, 30 Apr 2024 at 19:18, Lucas De Marchi <lucas.demarchi@intel.com> wrote:
> >>
> >> On Tue, Apr 30, 2024 at 06:54:00PM GMT, Emil Velikov wrote:
> >> >On Tue, 30 Apr 2024 at 18:39, Lucas De Marchi <lucas.demarchi@intel.com> wrote:
> >> >>
> >> >> On Mon, Feb 12, 2024 at 05:23:10PM GMT, Emil Velikov via B4 Relay wrote:
> >> >> >From: Emil Velikov <emil.l.velikov@gmail.com>
> >> >> >
> >> >> >Since all the compression magic is always available now, we don't need
> >> >> >to loop at runtime nor use alloca - latter of which comes with a handful
> >> >> >of caveats.
> >> >> >
> >> >> >Simply throw in a few assert_cc(), which will trigger at build-time.
> >> >> >
> >> >> >Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
> >> >> >---
> >> >> > libkmod/libkmod-file.c | 22 ++++++++--------------
> >> >> > 1 file changed, 8 insertions(+), 14 deletions(-)
> >> >> >
> >> >> >diff --git a/libkmod/libkmod-file.c b/libkmod/libkmod-file.c
> >> >> >index b69f1ef..5b88d6c 100644
> >> >> >--- a/libkmod/libkmod-file.c
> >> >> >+++ b/libkmod/libkmod-file.c
> >> >> >@@ -410,7 +410,6 @@ struct kmod_file *kmod_file_open(const struct kmod_ctx *ctx,
> >> >> > {
> >> >> >       struct kmod_file *file = calloc(1, sizeof(struct kmod_file));
> >> >> >       const struct comp_type *itr;
> >> >> >-      size_t magic_size_max = 0;
> >> >> >       int err = 0;
> >> >> >
> >> >> >       if (file == NULL)
> >> >> >@@ -422,22 +421,17 @@ struct kmod_file *kmod_file_open(const struct kmod_ctx *ctx,
> >> >> >               goto error;
> >> >> >       }
> >> >> >
> >> >> >-      for (itr = comp_types; itr->load != NULL; itr++) {
> >> >> >-              if (magic_size_max < itr->magic_size)
> >> >> >-                      magic_size_max = itr->magic_size;
> >> >> >-      }
> >> >> >-
> >> >> >-      if (magic_size_max > 0) {
> >> >> >-              char *buf = alloca(magic_size_max + 1);
> >> >> >+      {
> >> >> >+              char buf[7];
> >> >> >               ssize_t sz;
> >> >> >
> >> >> >-              if (buf == NULL) {
> >> >> >-                      err = -errno;
> >> >> >-                      goto error;
> >> >> >-              }
> >> >> >-              sz = read_str_safe(file->fd, buf, magic_size_max + 1);
> >> >> >+              assert_cc(sizeof(magic_zstd) < sizeof(buf));
> >> >> >+              assert_cc(sizeof(magic_xz) < sizeof(buf));
> >> >> >+              assert_cc(sizeof(magic_zlib) < sizeof(buf));
> >> >>
> >> >> ../libkmod/libkmod-file.c: In function 'kmod_file_open':
> >> >> ../shared/macro.h:25:9: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
> >> >
> >> >Is there a particular use-case for explicitly forcing C90?
> >>
> >> not forcing C90, but forcing -Wdeclaration-after-statement as per
> >> flag passed in configure.ac. I think the message given by gcc is
> >> misleading here.
> >>
> >
> >Indeed thanks. Seems like I should add `export CFLAGS+=-Werror" to my dev box.
>
> so, are you ok that I just squash this?
>

Yes, of course.

-Emil