[cfe-dev] -Warray-bounds seems over-zealous on Clang

[Andrew Fish]

On Jul 12, 2011, at 8:54 AM, Peter Geoghegan wrote:

> Saying "just use C99" isn't a practical solution. This is a mature
> project with a large codebase, that targets many compilers, including,
> for a large number of reasons, Visual Studio - Microsoft have
> absolutely no interest in pursuing C99 support.
> 

We have had the same problem in the EFI firmware open source project (edk2). The edk2 project supports Visual Studio 20XX, gcc, RVCT, clang, ...

> Besides, the chances of Clang actually helpfully diagnosing a problem
> with the delta between how GCC does -Warray-bounds and how Clang does
> it are slim - how often are these problems statically detectable? This
> is C.

We have found real bugs in chipset and driver code with clangs -Warray-bounds, that the other compilers did not find. 

So, given it is C, we just add a int *value = &A.value[0], and replace A.value[n] with value[n]. 

Luckily for us the case of the value[1] variable length array were mostly in regards to processing data structures from specifications and we had a single C function per instance that was doing the parsing. The changes were accepted to the open source project, so we did not have to turn off -Warray-bounds.

> 
> Even if your position wasn't unreasonable, which it is, Clang still
> gives this warning when the -c89 flag is given.
> 
> -- 
> Peter Geoghegan       http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Training and Services
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