[Webkit-unassigned] [Bug 174506] New: Silence -Wformat-truncation warning in ConfigFile.cpp

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=174506

            Bug ID: 174506
           Summary: Silence -Wformat-truncation warning in ConfigFile.cpp
           Product: WebKit
           Version: Other
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: Minor
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: mcatanzaro at igalia.com
            Blocks: 174463

This is another new GCC 7 warning.

[978/5861] Building CXX object Source/...criptCore.dir/runtime/ConfigFile.cpp.o
../../Source/JavaScriptCore/runtime/ConfigFile.cpp: In lambda function:
../../Source/JavaScriptCore/runtime/ConfigFile.cpp:281:62: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
     auto parseLogFile = [&](StatementNesting statementNesting) {
                                                              ^
../../Source/JavaScriptCore/runtime/ConfigFile.cpp:286:29: note: ‘snprintf’ output 2 or more bytes (assuming 4098) into a destination of size 4097
                     snprintf(logPathname, s_maxPathLength + 1, "%s/%s", m_configDirectory, filename);
                     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

                                                                             ^

The warning means that m_configDirectory could potentially consume as much as s_maxPathLength, followed by the trailing NULL, and then the / and the filename might not get printed. That seems like the most reasonable thing to do in this case, so I think that's fine and the warning should be suppressed. Unfortunately, compilers warn when they see unknown warning suppression pragmas, so the pattern for this is not pretty. I would almost prefer to use WTF::String instead, except all the rest of the code in this function uses cstring functions.


Referenced Bugs:

https://bugs.webkit.org/show_bug.cgi?id=174463
[Bug 174463] Fix compiler warnings when building with GCC 7
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