Re: [PATCH v8 2/6] util: Introduce read_file() and read_file_integer() function

[Stefano Brivio <sbrivio@redhat.com>]

On Mon, 17 Nov 2025 09:10:01 +0800
Yumei Huang <yuhuang@redhat.com> wrote:

> On Fri, Nov 14, 2025 at 6:12 PM Stefano Brivio <sbrivio@redhat.com> wrote:
> >
> > On Fri, 14 Nov 2025 09:58:57 +0800
> > Yumei Huang <yuhuang@redhat.com> wrote:
> >  
> > > On Fri, Nov 14, 2025 at 8:01 AM Stefano Brivio <sbrivio@redhat.com> wrote:  
> > > >
> > > > On Mon, 10 Nov 2025 17:31:33 +0800
> > > > Yumei Huang <yuhuang@redhat.com> wrote:
> > > >  
> > > > > Signed-off-by: Yumei Huang <yuhuang@redhat.com>
> > > > > Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> > > > > ---
> > > > >  util.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > > >  util.h |  2 ++
> > > > >  2 files changed, 88 insertions(+)
> > > > >
> > > > > diff --git a/util.c b/util.c
> > > > > index 44c21a3..c4c849c 100644
> > > > > --- a/util.c
> > > > > +++ b/util.c
> > > > > @@ -590,6 +590,92 @@ int write_file(const char *path, const char *buf)
> > > > >       return len == 0 ? 0 : -1;
> > > > >  }
> > > > >
> > > > > +/**
> > > > > + * read_file() - Read contents of file into a NULL-terminated buffer
> > > > > + * @path:    Path to file to read
> > > > > + * @buf:     Buffer to store file contents
> > > > > + * @buf_size:        Size of buffer
> > > > > + *
> > > > > + * Return: number of bytes read on success, -1 on error, -ENOBUFS on truncation
> > > > > + */
> > > > > +ssize_t read_file(const char *path, char *buf, size_t buf_size)
> > > > > +{
> > > > > +     int fd = open(path, O_RDONLY | O_CLOEXEC);
> > > > > +     size_t total_read = 0;
> > > > > +     ssize_t rc;
> > > > > +
> > > > > +     if (fd < 0) {
> > > > > +             warn_perror("Could not open %s", path);
> > > > > +             return -1;
> > > > > +     }
> > > > > +
> > > > > +     while (total_read < buf_size) {
> > > > > +             rc = read(fd, buf + total_read, buf_size - total_read);  
> > > >
> > > > cppcheck rightfully says that:
> > > >
> > > > util.c:604:10: style: The scope of the variable 'rc' can be reduced. [variableScope]
> > > >  ssize_t rc;
> > > >          ^  
> > >
> > > Right.
> > > Seems it also says:
> > >
> > > tcp.c:2814:0: style: The function 'tcp_get_rto_params' should have
> > > static linkage since it is not used outside of its translation unit.
> > > [staticFunction]
> > > void tcp_get_rto_params(struct ctx *c)
> > > ^
> > > util.c:601:0: style: The function 'read_file' should have static
> > > linkage since it is not used outside of its translation unit.
> > > [staticFunction]
> > > ssize_t read_file(const char *path, char *buf, size_t buf_size)  
> >
> > Oops, my current version (2.16.0) doesn't say that, I should upgrade it
> > (but I typically try to remain a few versions behind as David usually
> > upgrades right away, so that we catch also differences).
> >  
> > > I understand read_file() may be called from other places in the
> > > future. But do we need to add static now? I guess we need it for
> > > tcp_get_rto_params().  
> >
> > On top of what David said, I'm not sure if we'll ever need it in
> > tcp_get_rto_params(): I guess we'll always want to read integers there.  
> 
> I meant we need to add static for tcp_get_rto_params().

Ah, yes, right, that one too, it's not used outside of tcp.c (its
compilation unit).

-- 
Stefano