[Qemu-devel] [PATCH v5] cutils: Provide strchrnul

[Qemu-devel] [PATCH v5] cutils: Provide strchrnul

[Keno Fischer]

strchrnul is a GNU extension and thus unavailable on a number of targets.
In the review for a commit removing strchrnul from 9p, I was asked to
create a qemu_strchrnul helper to factor out this functionality.
Do so, and use it in a number of other places in the code base that inlined
the replacement pattern in a place where strchrnul could be used.

Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Acked-by: Greg Kurz <groug@kaod.org>
---

Changes since v4:
 - `CONFIG_STRCHRNUL` -> `HAVE_STRCHRNUL` name change
 - In the strchrnul configure check
   - Return the value of strchrnul to avoid it being optimized away
   - Use `&main` (i.e. the assembly of the generated function as
     the haystack) to avoid concerns about constant folding. `main`
     seemed like the simplest symbol guaranteed to exist, but with
     non-foldable content.

 configure             | 18 ++++++++++++++++++
 hmp.c                 |  8 ++++----
 hw/9pfs/9p-local.c    |  2 +-
 include/qemu/cutils.h |  8 ++++++++
 monitor.c             |  8 ++------
 util/cutils.c         | 15 +++++++++++++++
 util/qemu-option.c    |  6 +-----
 util/uri.c            |  6 ++----
 8 files changed, 51 insertions(+), 20 deletions(-)

diff --git a/configure b/configure
index 14b1113..8a75745 100755
--- a/configure
+++ b/configure
@@ -4747,6 +4747,21 @@ if compile_prog "" "" ; then
 fi
 
 ##########################################
+# check if we have strchrnul
+
+strchrnul=no
+cat > $TMPC << EOF
+#include <string.h>
+int main(void);
+// Use a haystack that the compiler shouldn't be able to constant fold
+char *haystack = (char*)&main;
+int main(void) { return strchrnul(haystack, 'x') != &haystack[6]; }
+EOF
+if compile_prog "" "" ; then
+    strchrnul=yes
+fi
+
+##########################################
 # check if trace backend exists
 
 $python "$source_path/scripts/tracetool.py" "--backends=$trace_backends" --check-backends  > /dev/null 2> /dev/null
@@ -6229,6 +6244,9 @@ fi
 if test "$sem_timedwait" = "yes" ; then
   echo "CONFIG_SEM_TIMEDWAIT=y" >> $config_host_mak
 fi
+if test "$strchrnul" = "yes" ; then
+  echo "HAVE_STRCHRNUL=y" >> $config_host_mak
+fi
 if test "$byteswap_h" = "yes" ; then
   echo "CONFIG_BYTESWAP_H=y" >> $config_host_mak
 fi
diff --git a/hmp.c b/hmp.c
index ef93f48..416d4c9 100644
--- a/hmp.c
+++ b/hmp.c
@@ -2123,12 +2123,12 @@ void hmp_sendkey(Monitor *mon, const QDict *qdict)
     int has_hold_time = qdict_haskey(qdict, "hold-time");
     int hold_time = qdict_get_try_int(qdict, "hold-time", -1);
     Error *err = NULL;
-    char *separator;
+    const char *separator;
     int keyname_len;
 
     while (1) {
-        separator = strchr(keys, '-');
-        keyname_len = separator ? separator - keys : strlen(keys);
+        separator = qemu_strchrnul(keys, '-');
+        keyname_len = separator - keys;
 
         /* Be compatible with old interface, convert user inputted "<" */
         if (keys[0] == '<' && keyname_len == 1) {
@@ -2165,7 +2165,7 @@ void hmp_sendkey(Monitor *mon, const QDict *qdict)
             keylist->value->u.qcode.data = idx;
         }
 
-        if (!separator) {
+        if (!*separator) {
             break;
         }
         keys = separator + 1;
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 5721eff..828e8d6 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -65,7 +65,7 @@ int local_open_nofollow(FsContext *fs_ctx, const char *path, int flags,
         assert(*path != '/');
 
         head = g_strdup(path);
-        c = strchrnul(path, '/');
+        c = qemu_strchrnul(path, '/');
         if (*c) {
             /* Intermediate path element */
             head[c - path] = 0;
diff --git a/include/qemu/cutils.h b/include/qemu/cutils.h
index a663340..274d419 100644
--- a/include/qemu/cutils.h
+++ b/include/qemu/cutils.h
@@ -122,6 +122,14 @@ int qemu_strnlen(const char *s, int max_len);
  * Returns: the pointer originally in @input.
  */
 char *qemu_strsep(char **input, const char *delim);
+#ifdef HAVE_STRCHRNUL
+static inline const char *qemu_strchrnul(const char *s, int c)
+{
+    return strchrnul(s, c);
+}
+#else
+const char *qemu_strchrnul(const char *s, int c);
+#endif
 time_t mktimegm(struct tm *tm);
 int qemu_fdatasync(int fd);
 int fcntl_setfl(int fd, int flag);
diff --git a/monitor.c b/monitor.c
index 6d0cec5..4484d74 100644
--- a/monitor.c
+++ b/monitor.c
@@ -797,9 +797,7 @@ static int compare_cmd(const char *name, const char *list)
     p = list;
     for(;;) {
         pstart = p;
-        p = strchr(p, '|');
-        if (!p)
-            p = pstart + strlen(pstart);
+        p = qemu_strchrnul(p, '|');
         if ((p - pstart) == len && !memcmp(pstart, name, len))
             return 1;
         if (*p == '\0')
@@ -3400,9 +3398,7 @@ static void cmd_completion(Monitor *mon, const char *name, const char *list)
     p = list;
     for(;;) {
         pstart = p;
-        p = strchr(p, '|');
-        if (!p)
-            p = pstart + strlen(pstart);
+        p = qemu_strchrnul(p, '|');
         len = p - pstart;
         if (len > sizeof(cmd) - 2)
             len = sizeof(cmd) - 2;
diff --git a/util/cutils.c b/util/cutils.c
index 0de69e6..9205e09 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -545,6 +545,21 @@ int qemu_strtou64(const char *nptr, const char **endptr, int base,
 }
 
 /**
+ * Searches for the first occurrence of 'c' in 's', and returns a pointer
+ * to the trailing null byte if none was found.
+ */
+#ifndef HAVE_STRCHRNUL
+const char *qemu_strchrnul(const char *s, int c)
+{
+    const char *e = strchr(s, c);
+    if (!e) {
+        e = s + strlen(s);
+    }
+    return e;
+}
+#endif
+
+/**
  * parse_uint:
  *
  * @s: String to parse
diff --git a/util/qemu-option.c b/util/qemu-option.c
index 58d1c23..54eca12 100644
--- a/util/qemu-option.c
+++ b/util/qemu-option.c
@@ -77,11 +77,7 @@ const char *get_opt_value(const char *p, char **value)
 
     *value = NULL;
     while (1) {
-        offset = strchr(p, ',');
-        if (!offset) {
-            offset = p + strlen(p);
-        }
-
+        offset = qemu_strchrnul(p, ',');
         length = offset - p;
         if (*offset != '\0' && *(offset + 1) == ',') {
             length++;
diff --git a/util/uri.c b/util/uri.c
index 8624a7a..8bdef84 100644
--- a/util/uri.c
+++ b/util/uri.c
@@ -52,6 +52,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/cutils.h"
 
 #include "qemu/uri.h"
 
@@ -2266,10 +2267,7 @@ struct QueryParams *query_params_parse(const char *query)
         /* Find the next separator, or end of the string. */
         end = strchr(query, '&');
         if (!end) {
-            end = strchr(query, ';');
-        }
-        if (!end) {
-            end = query + strlen(query);
+            end = qemu_strchrnul(query, ';');
         }
 
         /* Find the first '=' character between here and end. */
-- 
2.8.1

Re: [Qemu-devel] [PATCH v5] cutils: Provide strchrnul

[Markus Armbruster]

Keno Fischer <keno@juliacomputing.com> writes:

> strchrnul is a GNU extension and thus unavailable on a number of targets.
> In the review for a commit removing strchrnul from 9p, I was asked to
> create a qemu_strchrnul helper to factor out this functionality.
> Do so, and use it in a number of other places in the code base that inlined
> the replacement pattern in a place where strchrnul could be used.
>
> Signed-off-by: Keno Fischer <keno@juliacomputing.com>
> Acked-by: Greg Kurz <groug@kaod.org>

Reviewed-by: Markus Armbruster <armbru@redhat.com>

Re: [Qemu-devel] [PATCH v5] cutils: Provide strchrnul

[Greg Kurz]

On Wed, 13 Jun 2018 07:42:57 +0200
Markus Armbruster <armbru@redhat.com> wrote:

> Keno Fischer <keno@juliacomputing.com> writes:
> 
> > strchrnul is a GNU extension and thus unavailable on a number of targets.
> > In the review for a commit removing strchrnul from 9p, I was asked to
> > create a qemu_strchrnul helper to factor out this functionality.
> > Do so, and use it in a number of other places in the code base that inlined
> > the replacement pattern in a place where strchrnul could be used.
> >
> > Signed-off-by: Keno Fischer <keno@juliacomputing.com>
> > Acked-by: Greg Kurz <groug@kaod.org>  
> 
> Reviewed-by: Markus Armbruster <armbru@redhat.com>

Maybe I can take this through my 9p-next tree since it is a pre-requisite
for the Darwin support series ?

Keno,

BTW, if you want Darwin support to go in the next QEMU release, please
pay attention that I have to send a pull req for it before 2018-07-03.

https://wiki.qemu.org/Planning/3.0

Cheers,

--
Greg

Re: [Qemu-devel] [PATCH v5] cutils: Provide strchrnul

[Markus Armbruster]

Greg Kurz <groug@kaod.org> writes:

> On Wed, 13 Jun 2018 07:42:57 +0200
> Markus Armbruster <armbru@redhat.com> wrote:
>
>> Keno Fischer <keno@juliacomputing.com> writes:
>> 
>> > strchrnul is a GNU extension and thus unavailable on a number of targets.
>> > In the review for a commit removing strchrnul from 9p, I was asked to
>> > create a qemu_strchrnul helper to factor out this functionality.
>> > Do so, and use it in a number of other places in the code base that inlined
>> > the replacement pattern in a place where strchrnul could be used.
>> >
>> > Signed-off-by: Keno Fischer <keno@juliacomputing.com>
>> > Acked-by: Greg Kurz <groug@kaod.org>  
>> 
>> Reviewed-by: Markus Armbruster <armbru@redhat.com>
>
> Maybe I can take this through my 9p-next tree since it is a pre-requisite
> for the Darwin support series ?

Go ahead :)

[...]

Re: [Qemu-devel] [PATCH v5] cutils: Provide strchrnul

[Greg Kurz]

On Tue, 12 Jun 2018 23:48:31 -0400
Keno Fischer <keno@juliacomputing.com> wrote:

> strchrnul is a GNU extension and thus unavailable on a number of targets.
> In the review for a commit removing strchrnul from 9p, I was asked to
> create a qemu_strchrnul helper to factor out this functionality.
> Do so, and use it in a number of other places in the code base that inlined
> the replacement pattern in a place where strchrnul could be used.
> 
> Signed-off-by: Keno Fischer <keno@juliacomputing.com>
> Acked-by: Greg Kurz <groug@kaod.org>
> ---
> 

Applied to 9p-next. You can rebase your patches against:

https://github.com/gkurz/qemu/commits/9p-next

Thanks!

> Changes since v4:
>  - `CONFIG_STRCHRNUL` -> `HAVE_STRCHRNUL` name change
>  - In the strchrnul configure check
>    - Return the value of strchrnul to avoid it being optimized away
>    - Use `&main` (i.e. the assembly of the generated function as
>      the haystack) to avoid concerns about constant folding. `main`
>      seemed like the simplest symbol guaranteed to exist, but with
>      non-foldable content.
> 
>  configure             | 18 ++++++++++++++++++
>  hmp.c                 |  8 ++++----
>  hw/9pfs/9p-local.c    |  2 +-
>  include/qemu/cutils.h |  8 ++++++++
>  monitor.c             |  8 ++------
>  util/cutils.c         | 15 +++++++++++++++
>  util/qemu-option.c    |  6 +-----
>  util/uri.c            |  6 ++----
>  8 files changed, 51 insertions(+), 20 deletions(-)
> 
> diff --git a/configure b/configure
> index 14b1113..8a75745 100755
> --- a/configure
> +++ b/configure
> @@ -4747,6 +4747,21 @@ if compile_prog "" "" ; then
>  fi
>  
>  ##########################################
> +# check if we have strchrnul
> +
> +strchrnul=no
> +cat > $TMPC << EOF
> +#include <string.h>
> +int main(void);
> +// Use a haystack that the compiler shouldn't be able to constant fold
> +char *haystack = (char*)&main;
> +int main(void) { return strchrnul(haystack, 'x') != &haystack[6]; }
> +EOF
> +if compile_prog "" "" ; then
> +    strchrnul=yes
> +fi
> +
> +##########################################
>  # check if trace backend exists
>  
>  $python "$source_path/scripts/tracetool.py" "--backends=$trace_backends" --check-backends  > /dev/null 2> /dev/null
> @@ -6229,6 +6244,9 @@ fi
>  if test "$sem_timedwait" = "yes" ; then
>    echo "CONFIG_SEM_TIMEDWAIT=y" >> $config_host_mak
>  fi
> +if test "$strchrnul" = "yes" ; then
> +  echo "HAVE_STRCHRNUL=y" >> $config_host_mak
> +fi
>  if test "$byteswap_h" = "yes" ; then
>    echo "CONFIG_BYTESWAP_H=y" >> $config_host_mak
>  fi
> diff --git a/hmp.c b/hmp.c
> index ef93f48..416d4c9 100644
> --- a/hmp.c
> +++ b/hmp.c
> @@ -2123,12 +2123,12 @@ void hmp_sendkey(Monitor *mon, const QDict *qdict)
>      int has_hold_time = qdict_haskey(qdict, "hold-time");
>      int hold_time = qdict_get_try_int(qdict, "hold-time", -1);
>      Error *err = NULL;
> -    char *separator;
> +    const char *separator;
>      int keyname_len;
>  
>      while (1) {
> -        separator = strchr(keys, '-');
> -        keyname_len = separator ? separator - keys : strlen(keys);
> +        separator = qemu_strchrnul(keys, '-');
> +        keyname_len = separator - keys;
>  
>          /* Be compatible with old interface, convert user inputted "<" */
>          if (keys[0] == '<' && keyname_len == 1) {
> @@ -2165,7 +2165,7 @@ void hmp_sendkey(Monitor *mon, const QDict *qdict)
>              keylist->value->u.qcode.data = idx;
>          }
>  
> -        if (!separator) {
> +        if (!*separator) {
>              break;
>          }
>          keys = separator + 1;
> diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
> index 5721eff..828e8d6 100644
> --- a/hw/9pfs/9p-local.c
> +++ b/hw/9pfs/9p-local.c
> @@ -65,7 +65,7 @@ int local_open_nofollow(FsContext *fs_ctx, const char *path, int flags,
>          assert(*path != '/');
>  
>          head = g_strdup(path);
> -        c = strchrnul(path, '/');
> +        c = qemu_strchrnul(path, '/');
>          if (*c) {
>              /* Intermediate path element */
>              head[c - path] = 0;
> diff --git a/include/qemu/cutils.h b/include/qemu/cutils.h
> index a663340..274d419 100644
> --- a/include/qemu/cutils.h
> +++ b/include/qemu/cutils.h
> @@ -122,6 +122,14 @@ int qemu_strnlen(const char *s, int max_len);
>   * Returns: the pointer originally in @input.
>   */
>  char *qemu_strsep(char **input, const char *delim);
> +#ifdef HAVE_STRCHRNUL
> +static inline const char *qemu_strchrnul(const char *s, int c)
> +{
> +    return strchrnul(s, c);
> +}
> +#else
> +const char *qemu_strchrnul(const char *s, int c);
> +#endif
>  time_t mktimegm(struct tm *tm);
>  int qemu_fdatasync(int fd);
>  int fcntl_setfl(int fd, int flag);
> diff --git a/monitor.c b/monitor.c
> index 6d0cec5..4484d74 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -797,9 +797,7 @@ static int compare_cmd(const char *name, const char *list)
>      p = list;
>      for(;;) {
>          pstart = p;
> -        p = strchr(p, '|');
> -        if (!p)
> -            p = pstart + strlen(pstart);
> +        p = qemu_strchrnul(p, '|');
>          if ((p - pstart) == len && !memcmp(pstart, name, len))
>              return 1;
>          if (*p == '\0')
> @@ -3400,9 +3398,7 @@ static void cmd_completion(Monitor *mon, const char *name, const char *list)
>      p = list;
>      for(;;) {
>          pstart = p;
> -        p = strchr(p, '|');
> -        if (!p)
> -            p = pstart + strlen(pstart);
> +        p = qemu_strchrnul(p, '|');
>          len = p - pstart;
>          if (len > sizeof(cmd) - 2)
>              len = sizeof(cmd) - 2;
> diff --git a/util/cutils.c b/util/cutils.c
> index 0de69e6..9205e09 100644
> --- a/util/cutils.c
> +++ b/util/cutils.c
> @@ -545,6 +545,21 @@ int qemu_strtou64(const char *nptr, const char **endptr, int base,
>  }
>  
>  /**
> + * Searches for the first occurrence of 'c' in 's', and returns a pointer
> + * to the trailing null byte if none was found.
> + */
> +#ifndef HAVE_STRCHRNUL
> +const char *qemu_strchrnul(const char *s, int c)
> +{
> +    const char *e = strchr(s, c);
> +    if (!e) {
> +        e = s + strlen(s);
> +    }
> +    return e;
> +}
> +#endif
> +
> +/**
>   * parse_uint:
>   *
>   * @s: String to parse
> diff --git a/util/qemu-option.c b/util/qemu-option.c
> index 58d1c23..54eca12 100644
> --- a/util/qemu-option.c
> +++ b/util/qemu-option.c
> @@ -77,11 +77,7 @@ const char *get_opt_value(const char *p, char **value)
>  
>      *value = NULL;
>      while (1) {
> -        offset = strchr(p, ',');
> -        if (!offset) {
> -            offset = p + strlen(p);
> -        }
> -
> +        offset = qemu_strchrnul(p, ',');
>          length = offset - p;
>          if (*offset != '\0' && *(offset + 1) == ',') {
>              length++;
> diff --git a/util/uri.c b/util/uri.c
> index 8624a7a..8bdef84 100644
> --- a/util/uri.c
> +++ b/util/uri.c
> @@ -52,6 +52,7 @@
>   */
>  
>  #include "qemu/osdep.h"
> +#include "qemu/cutils.h"
>  
>  #include "qemu/uri.h"
>  
> @@ -2266,10 +2267,7 @@ struct QueryParams *query_params_parse(const char *query)
>          /* Find the next separator, or end of the string. */
>          end = strchr(query, '&');
>          if (!end) {
> -            end = strchr(query, ';');
> -        }
> -        if (!end) {
> -            end = query + strlen(query);
> +            end = qemu_strchrnul(query, ';');
>          }
>  
>          /* Find the first '=' character between here and end. */