Make it obvious to the compiler that nullptr format string is not possible

2 files changed, 5 insertions, 2 deletions

diff --git a/fastos/src/tests/threadtest.cpp b/fastos/src/tests/threadtest.cpp
index de1e15de2b3..968779019cb 100644
--- a/fastos/src/tests/threadtest.cpp
+++ b/fastos/src/tests/threadtest.cpp
@@ -28,6 +28,9 @@ class ThreadTest : public ThreadTestBase
          for (i=0; i<MAX_THREADS+1; i++) {
             jobs[i].code = WAIT_FOR_BREAK_FLAG;
             jobs[i].message = static_cast<char *>(malloc(100));
+            if (jobs[i].message == nullptr) {
+                abort(); // GCC may infer that a potentially null ptr is passed to sprintf
+            }
             sprintf(jobs[i].message, "Thread %d invocation", i+1);
          }
 
diff --git a/vespalib/src/vespa/vespalib/data/slime/strfmt.h b/vespalib/src/vespa/vespalib/data/slime/strfmt.h
index e1a24ce505d..01e60eac3c0 100644
--- a/vespalib/src/vespa/vespalib/data/slime/strfmt.h
+++ b/vespalib/src/vespa/vespalib/data/slime/strfmt.h
@@ -8,8 +8,8 @@ namespace vespalib::slime {
 
 extern std::string strfmt(const char *fmt, ...)
 #ifdef __GNUC__
-        // Add printf format checks with gcc
-        __attribute__ ((format (printf,1,2)))
+        __attribute__ ((format (printf,1,2))) // Add printf format checks with gcc
+        __attribute__((nonnull(1))) // Format string can never be null
 #endif
     ;