Fixed corrupt testlogs on Windows and other places where vsnprintf is

not C99-compliant.

C99 says vsnprintf returns >= `size' when not enough memory was
available.  In practice, on Windows, glibc < 2.0.6, and probably plenty
of other places it returns -1 instead.

Reviewed-by: Rhys Weatherley

1 files changed, 4 insertions, 3 deletions

diff --git a/src/testlib/qtestcase.cpp b/src/testlib/qtestcase.cpp
index e44be9cec..1dae828b4 100644
--- a/src/testlib/qtestcase.cpp
+++ b/src/testlib/qtestcase.cpp
@@ -834,11 +834,12 @@ int qt_asprintf(char **str, const char *format, ...)
         res = qvsnprintf(*str, size, format, ap);
         va_end(ap);
         (*str)[size - 1] = '\0';
-        if (res < size) {
-            // We succeeded or fatally failed
+        if (res >= 0 && res < size) {
+            // We succeeded
             break;
         }
-        // buffer wasn't big enough, try again
+        // buffer wasn't big enough, try again.
+        // Note, we're assuming that a result of -1 is always due to running out of space.
         size *= 2;
         if (size > MAXSIZE) {
             break;