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Re: [libvirt] [PATCH] [v2] Support kvm-img or qemu-img dynamically



2009/6/10 Doug Goldstein <cardoe gentoo org>:
> This patch adds a new function virFindFileInPath() and uses it to find
> where a binary lives in the PATH environment variable. [...]

+/*

+ * Finds a requested file in the PATH env. e.g.:

+ * "kvm-img" will return "/usr/bin/kvm-img"

+ *

+ * You must free the result

+ */

+char *virFindFileInPath(const char *file)

+{

+    char pathenv[PATH_MAX];

+    char *penv = &pathenv; /* this is for glibc 2.10 strsep chnages */

+    char *pathseg;

+    char fullpath[PATH_MAX];

+

+    /* copy PATH env so we can tweak it */

+    strncpy(pathenv, getenv("PATH"), PATH_MAX);

+    pathenv[PATH_MAX - 1] = '\0';

+

+    /* for each path segment, append the file to search for and test for

+     * it. return it if found.

+     */

+    while ((pathseg = strsep(&penv, ":")) != NULL) {

+       snprintf(fullpath, PATH_MAX, "%s/%s", pathseg, file);

+       if (virFileExists(fullpath))

+           return strdup(fullpath);

+    }

+

+    return NULL;

+}

GCC (version 4.3.3 here) warns about "initialization from incompatible
pointer type" at this line:

char *penv = &pathenv; /* this is for glibc 2.10 strsep chnages */

Changing it to

char *penv = pathenv; /* this is for glibc 2.10 strsep chnages */

fixes the warning.

At first I was surprised that the first version with & works and gives
correct results, then I checked that actual values that are assigned
to char *penv and it's the same in both cases. But the point is: the
additional & triggers a warning (breaks compilation with
--enable-compile-warnings=error) and removing it doesn't change the
behavior.

PS: What's this comment about changes in glibc 2.10 to strsep()
referring to? I looked at the changelog but couldn't find any recent
changes to strsep().

Regards,
  Matthias


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