[R-pkg-devel] building on CRAN: GCC 12 truncation warning, attempted fix not working

[Simon Urbanek]

Gillian,

the buffer has to have enough space for the content *and* a terminating NUL character, so you need total of at least 12 bytes. Given that stack is typically aligned at 8-bytes I'd simply use 16 for safety.

Cheers,
Simon



> On Mar 24, 2022, at 11:04 AM, Gillian Sharer <gillian using iris.washington.edu> wrote:
> 
> We have some C code in our IRISSeismic package that has starting generating truncation warnings with GCC 12. 
> 
> This is the original code and warning: 
> 
> 
> char seqnum[7]; 
> 
> snprintf (seqnum, 7, "%06d", msr->sequence_number); 
> 
> 
> 
> 
> warning: ' %06d' directive output may be truncated writing between 6 and 11 bytes into a region of size 7 [-Wformat-truncation=] 
> 
> 
> 
> 
> This was our attempted fix and new warning: 
> 
> char seqnum[11]; 
> 
> snprintf (seqnum, sizeof(seqnum), "%06d", msr->sequence_number); 
> 
> 
> 
> 
> warning: ' snprintf' output may be truncated before the last format character [-Wformat-truncation=] 
> 
> 
> 
> 
> I don't have much experience with C and I'm not sure why the attempted fix didn't work. Does anyone have advice on what else I can try to fix this? 
> 
> 
> 
> 
> 
> Thanks, 
> 
> Gillian Sharer 
> 
> IRIS DMC 
> 
> 
> 
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