[libvirt] [PATCH 05/11] util: use glib string allocation/formatting functions

[Pavel Hrdina]

On Fri, Sep 27, 2019 at 06:17:27PM +0100, Daniel P. Berrangé wrote:
> Convert the string duplication APIs to use the g_strdup family of APIs.
> 
> Annoyingly our virVasprintf/virAsprintf functions return the character
> count, even though 90% of our usage doesn't need it. To retain compat
> with these semantics we have a call to strlen which costs CPU time.
> 
> We previously used the 'strdup-posix' gnulib module because mingw does
> not set errno to ENOMEM on failure
> 
> We previously used the 'strndup' gnulib module because this function
> does not exist on mingw.
> 
> We previously used the 'vasprintf' gnulib module because of many GNU
> supported format specifiers not working on non-Linux platforms. glib's
> own equivalent standardizes on GNU format specifiers too.
> 
> Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> ---
>  bootstrap.conf       |  3 ---
>  src/util/virstring.c | 19 +++++++------------
>  2 files changed, 7 insertions(+), 15 deletions(-)
> 
> diff --git a/bootstrap.conf b/bootstrap.conf
> index 549d18c6d4..b6b75f9301 100644
> --- a/bootstrap.conf
> +++ b/bootstrap.conf
> @@ -100,8 +100,6 @@ stat-time
>  stdarg
>  stpcpy
>  strchrnul
> -strdup-posix
> -strndup
>  strerror
>  strerror_r-posix
>  strptime
> @@ -117,7 +115,6 @@ uname
>  unsetenv
>  useless-if-before-free
>  usleep
> -vasprintf
>  verify
>  vc-list-files
>  vsnprintf
> diff --git a/src/util/virstring.c b/src/util/virstring.c
> index a4cc7e9c0a..c8c888b2a0 100644
> --- a/src/util/virstring.c
> +++ b/src/util/virstring.c
> @@ -730,12 +730,9 @@ virVasprintfInternal(char **strp,
>                       const char *fmt,
>                       va_list list)
>  {
> -    int ret;
> +    *strp = g_strdup_vprintf(fmt, list);
>  
> -    if ((ret = vasprintf(strp, fmt, list)) == -1)
> -        abort();
> -
> -    return ret;
> +    return strlen(*strp);

This will cause a SEGFAULT if strp is NULL as g_strdup_vprintf doesn't
abort on failure.

We can use g_vasprintf which returns length.

But if we want to return only -1 or 0 and let the caller to decide on
the length there are only few places to modify.

    src/nwfilter/nwfilter_dhcpsnoop.c:1770
    src/util/virfile.c:3410

These two looks like the only cases where we actually care about the
length.  There are some other cases for which we would have to only
tweak to comparison:

    src/libxl/libxl_domain.c:916:

There is a function virDoubleToStr that returns the length but it's
usage doesn't care about the length so we would have to change the
description.

Pavel
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20190930/c74b1f46/attachment-0001.sig>