Fix: Integer Overflow in OptionConverter & Enable >2GB logs on Windows #585
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Changed toFileSize signature to return 'long long' instead of 'long'. On Windows (LLP64), 'long' is 32-bit, causing overflow for sizes >= 2GB. Using 'long long' guarantees 64-bit width, preventing negative file sizes and enabling support for large log files.
Restored original 'long toFileSize' signature to preserve binary compatibility. Added new 'toFileSize64' method for 64-bit support. Old method now wraps the new one with safety clamping to prevent overflow.
rm5248
reviewed
Jan 29, 2026
| and gigabytes. For example, the value "10KB" will be interpreted as 10240. | ||
| */ | ||
| /** | ||
| * @deprecated Use toFileSize64 instead. |
Contributor
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this should use the newer [[deprecated]] annotation like is used in other places(example:
| * The numeric equivalent of \c value if it is not empty, otherwise \c defaultValue. | ||
| * Supports 64-bit values for file sizes > 2GB. | ||
| */ | ||
| static long long toFileSize64(const LogString& value, long long defaultValue); |
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@swebb2066 any thoughts on long long vs. int64_t? The latter is used in a few parts of the API, but they should both be equivalent.
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I went with long long just to be safe on Windows (LLP64), but I see int64_t is used elsewhere. I can switch to that for consistency if you prefer.
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any thoughts on long long vs. int64_t
I prefer int64_t for its explicit size and the single word
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Summary
I identified a platform-dependent integer overflow in
OptionConverter::toFileSize.The library previously used
longfor file size calculations. On Windows (MSVC),longis strictly 32-bit (LLP64 data model), whereas it is 64-bit on Linux (LP64).The Issue:
Configuring
MaxFileSize="3GB"on Windows triggers a signed integer overflow:3 * 1024^3=3,221,225,472-> wraps to-1,073,741,824(negative).This negative value is passed to RollingFileAppender, causing logic errors (DoS via infinite rotation or rotation failure).
The Fix:
I updated the API signature in
optionconverter.hand the implementation inoptionconverter.cppto uselong long(guaranteed 64-bit on all platforms) and leveragedStringHelper::toInt64.Impact