[Bug tree-optimization/78696] [7 Regression] -fprintf-return-value misoptimizes %.Ng where N is greater than 10

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78696

--- Comment #9 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Implementation-specific can in practice include cases where the 
implementation deviates from the standard (e.g. Windows 3-digit exponents, 
though disabling the optimization for floating-point formats should hide 
that).  It's clearly not a good idea to convert a minor conformance bug in 
the library into a buffer overrun by causing a program to allocate enough 
memory for the standard output from a format but not enough for what the 
library implementation actually outputs.

(It wouldn't surprise me if there are printf implementations whose results 
for some floating-point values are not one of the nearest decimals in each 
direction and so could take more characters than either of those take in 
some cases.)