Question

Consider the following. Why does sizeof return “23”? And how can I get the real size? (without counting heh)

char defaultsettings[] = "<?xml version=\"1.0\"?>\n";
strcat(defaultsettings, "<CsSettings>\n<options>\n");
strcat(defaultsettings, "<spin name=\"maxTries\" value=\"1000\" />\n");
strcat(defaultsettings, "<spin name=\"rollCount\" value=\"1\" />\n");
strcat(defaultsettings, "<check name=\"matchItems\" value=\"1\" />\n");
strcat(defaultsettings, "<check name=\"highlightItems\" value=\"1\" />\n");
strcat(defaultsettings, "<check name=\"buyListMode\" value=\"0\" />\n");
strcat(defaultsettings, "<radio name=\"matchItemType\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"matchLocations\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"highlightLocations\" value=\"1\" />\n");
strcat(defaultsettings, "<check name=\"allMissionsSameLocation\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"highlightFind\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"highlightReturn\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"highlightRepair\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"highlightPerson\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"highlightKill\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"ignoreFind\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"ignoreReturn\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"ignoreRepair\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"ignorePerson\" value=\"0\" />\n");
strcat(defaultsettings, "<check name=\"ignoreKill\" value=\"1\" />\n");
strcat(defaultsettings, "<combo name=\"itemValueBase\" value=\"1\" />\n");
strcat(defaultsettings, "<check name=\"matchMissionValue\" value=\"0\" />\n");
strcat(defaultsettings, "<spin name=\"matchMissionMinValue\" value=\"10000\" />\n");
strcat(defaultsettings, "<check name=\"levelCalcFixerMode\" value=\"0\" />\n");
strcat(defaultsettings, "<spin name=\"bneBonus\" value=\"1\" />\n");
strcat(defaultsettings, "<spin name=\"levelCalc\" value=\"1\" />\n");
strcat(defaultsettings, "<spin name=\"missionCalc\" value=\"1\" />\n");
strcat(defaultsettings, "<check name=\"log\" value=\"0\" />\n");
strcat(defaultsettings, "<entry name=\"useKey\" value=\"e\" />\n");
strcat(defaultsettings, "</options>\n<items>\n</items>\n");
strcat(defaultsettings, "<locations>\n<location>\n<string>Milky way</string>\n");
strcat(defaultsettings, "<x>\n<var>3050</var>\n<var>3400</var>\n</x>\n");
strcat(defaultsettings, "<y>\n<var>1000</var>\n<var>1200</var>\n</y>\n");
strcat(defaultsettings, "<ignore>1</ignore>\n<enabled>1</enabled>\n");
strcat(defaultsettings, "<coordsEnabled>1</coordsEnabled>\n");
strcat(defaultsettings, "</location>\n<location>\n<string>Milky way</string>\n");
strcat(defaultsettings, "<x>\n<var>3500</var>\n<var>3850</var>\n</x>\n");
strcat(defaultsettings, "<y>\n<var>700</var>\n<var>950</var>\n</y>\n");
strcat(defaultsettings, "<ignore>1</ignore>\n<enabled>1</enabled>\n");
strcat(defaultsettings, "<coordsEnabled>1</coordsEnabled>\n");
strcat(defaultsettings, "</location>\n</locations>\n</CsSettings>");
printf("%s\nSize: %d\n\n",defaultsettings,sizeof(defaultsettings));

Output:

[...]
</location>
</locations>
</CsSettings>
Size: 23

Answer 1

Oh dear!

Because you have only allocated memory for 23 chars on the first line, and are then overwriting unallocated memory for the rest of the data.

You don’t actually need any of the strcat’s here, you can just use a feature of then C preprocessor that concatenates adjacent string literals:

const char long_string[]  = "First line"
"next line"
"another line"
"even more text";

This will get you one array of the proper size.