Build failure with -Werror=lto-type-mismatch (LTO)

This was reported on Gentoo at https://bugs.gentoo.org/878987, and I've verified that it still happens with the latest v0.3.23.

The -Wlto-type-mismatch flag warns about type mismatches in global declarations from different compilation units. The "lto" part is because those mismatches are dangerous in the presence of LTO, and the warnings are enabled by default with -flto. Adding -Werror=lto-type-mismatch moreover turns them into errors, so that said code cannot sneak into an LTO build. To reproduce, set CFLAGS="-flto -Werror=lto-type-mismatch" and build OpenBLAS.

For background, on Gentoo, users are likely to set CFLAGS="-flto" globally and then add CFLAGS+=" -Werror=lto-type-mismatch" as a safety net against miscompiled packages. On such a machine OpenBLAS will fail to build. As one of the maintainers, I could disable LTO wholesale, but of course it would be preferable (if not to difficult) to just fix the mismatches.

Riproduci la build di OpenBLAS con CFLAGS="-flto -Werror=lto-type-mismatch" come descritto nell’issue, quindi esamina i diagnostici del compilatore alla ricerca di dichiarazioni globali non corrispondenti tra le unità di compilazione. Traccia ogni dichiarazione segnalata fino ai relativi sorgenti C e verifica che la build vada a buon fine con i flags una volta risolte le discrepanze.