[Xen-devel] [PATCH 1/2] libxl: fix _SC_GETPW_R_SIZE_MAX usage

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

According to the FreeBSD sysconf man page [0] if the variable is associated
with functionality that is not supported, -1 is returned and errno is not
modified. Modify libxl__dm_runas_helper so it's able to correctly
deal with this situation by setting the initial buffer value to 2048.

[0] https://www.freebsd.org/cgi/man.cgi?query=sysconf

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
---
 tools/libxl/libxl_dm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 0aaefd9..ec8fb51 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -728,7 +728,14 @@ static int libxl__dm_runas_helper(libxl__gc *gc, const 
char *username)
     long buf_size;
     int ret;
 
+    errno = 0;
     buf_size = sysconf(_SC_GETPW_R_SIZE_MAX);
+    if (buf_size < 0 && errno == 0) {
+        buf_size = 2048;
+        LOG(DEBUG,
+"sysconf(_SC_GETPW_R_SIZE_MAX) is not supported, using a buffer size of %ld",
+            buf_size);
+    }
     if (buf_size < 0) {
         LOGE(ERROR, "sysconf(_SC_GETPW_R_SIZE_MAX) returned error %ld",
                 buf_size);
-- 
1.9.5 (Apple Git-50.3)


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