BUG: Do not write to the stream that failed to open

cifti/CMakeLists.txt

@@ -68,4 +68,14 @@ if(NIFTI_BUILD_TESTING AND NIFTI_BUILD_APPLICATIONS)
                     -input ${CMAKE_CURRENT_LIST_DIR}/testdata/deep_nesting.xml )
   set_tests_properties( ${TEST_PREFIX}_deep_nesting
             PROPERTIES PASS_REGULAR_EXPRESSION "BrainModel" )
+
+  # A -output path that cannot be opened must be reported and refused, not
+  # written to anyway.
+  add_test( NAME ${TEST_PREFIX}_write_failure
+            COMMAND ${CMAKE_COMMAND}
+                    -DTOOL=$<TARGET_FILE:${NIFTI_PACKAGE_PREFIX}cifti_tool>
+                    -DINPUT=${CMAKE_CURRENT_LIST_DIR}/testdata/cext_unterminated.nii
+                    -DBADOUT=${CMAKE_CURRENT_BINARY_DIR}/no_such_dir/out.txt
+                    -DGOODOUT=${CMAKE_CURRENT_BINARY_DIR}/write_failure_ok.txt
+                    -P ${CMAKE_CURRENT_LIST_DIR}/test_write_failure.cmake )
 endif()

cifti/cifti_tool.c

@@ -219,6 +219,7 @@ int disp_cifti_extension(nifti_image * nim, opts_t * opts)
       }
 
    fp = open_write_stream(opts->fout);
+   if( !fp ) return 1;   /* open_write_stream() has reported the failure */
    if( !ext ) {
       fprintf(fp, "** no CIFTI extension in %s\n",nim->fname?nim->fname:"NULL");
       close_stream(fp);
@@ -242,6 +243,7 @@ int eval_cifti_extension(afni_xml_t * ax, opts_t * opts)
               opts->fout ? opts->fout : "DEFAULT" );
 
    fp = open_write_stream(opts->fout);
+   if( !fp ) return 1;   /* open_write_stream() has reported the failure */
    axml_set_wstream(fp);
 
    if( opts->verb > 1 ) fprintf(stderr, "-- recursive eval from %s\n",

cifti/test_write_failure.cmake

@@ -0,0 +1,42 @@
+# Drives cifti_tool at an unopenable -output path.  A plain add_test cannot
+# express this: PASS_REGULAR_EXPRESSION ignores the exit status, so a crash
+# that printed the diagnostic first would still pass.
+
+if(NOT TOOL OR NOT INPUT OR NOT BADOUT OR NOT GOODOUT)
+  message(FATAL_ERROR "TOOL, INPUT, BADOUT and GOODOUT are all required")
+endif()
+
+function(run_tool expect_result out_var)
+  execute_process(COMMAND ${TOOL} ${ARGN}
+                  RESULT_VARIABLE result
+                  OUTPUT_VARIABLE out
+                  ERROR_VARIABLE err)
+  set(${out_var} "${out}${err}" PARENT_SCOPE)
+  if(NOT result STREQUAL "${expect_result}")
+    message(FATAL_ERROR
+            "expected result ${expect_result}, got '${result}'\n${out}${err}")
+  endif()
+endfunction()
+
+run_tool(0 bad_disp -input ${INPUT} -disp_cext -output ${BADOUT})
+if(NOT bad_disp MATCHES "failed to open")
+  message(FATAL_ERROR "missing the open-failure diagnostic:\n${bad_disp}")
+endif()
+
+run_tool(0 bad_eval -input ${INPUT} -eval_cext -eval_type show_summary
+                    -output ${BADOUT})
+if(NOT bad_eval MATCHES "failed to open")
+  message(FATAL_ERROR "missing the open-failure diagnostic:\n${bad_eval}")
+endif()
+
+# An openable -output must still be written, so that refusing every write
+# would not pass.
+file(REMOVE ${GOODOUT})
+run_tool(0 good_disp -input ${INPUT} -disp_cext -output ${GOODOUT})
+if(NOT EXISTS ${GOODOUT})
+  message(FATAL_ERROR "nothing written to ${GOODOUT}")
+endif()
+file(READ ${GOODOUT} written)
+if(NOT written MATCHES "MapName")
+  message(FATAL_ERROR "extension not displayed:\n${written}")
+endif()