string truncation

Detecting String Truncation with GCC 8

Detecting String Truncation with GCC 8

Continuing in the effort to detect common programming errors, the just-released GCC 8 contains a number of new warnings as well as enhancements to existing checkers to help find non-obvious bugs in C and C++ code. This article focuses on those that deal with inadvertent string truncation and discusses some of the approaches for avoiding the underlying problems. If you haven’t read it, you might also want to read David Malcolm’s article Usability improvements in GCC 8.

To use GCC 8 on RHEL, see How to install GCC 8 and Clang/LLVM 6 on Red Hat Enterprise Linux 7.  GCC 8 is the default compiler in Red Hat Enterprise Linux 8 Beta.

Why Is String Truncation a Problem?

It is well-known why buffer overflow is dangerous: writing past the end of an object can overwrite data in adjacent storage, resulting in data corruption. In the most benign cases, the corruption can simply lead to incorrect behavior of the program. If the adjacent data is an address in the executable text segment, the corruption may be exploitable to gain control of the affected process, which can lead to a security vulnerability. (See CWE-119 for more on buffer overflow.)

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