[Bug middle-end/78153] strlen return value can be assumed to be less than PTRDIFF_MAX

[schwab@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78153

--- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> ---
This breaks ada on aarch64:

/opt/gcc/gcc-20161124/Build/./prev-gcc/xgcc
-B/opt/gcc/gcc-20161124/Build/./prev-gcc/ -B/usr/aarch64-suse-linux/bin/
-B/usr/aarch64-suse-linux/bin/ -B/usr/aarch64-suse-linux/lib/ -isystem
/usr/aarch64-suse-linux/include -isystem /usr/aarch64-suse-linux/sys-include   
-c -g -O2 -gtoggle  -gnatpg -gnata -W -Wall -nostdinc -I- -I. -Iada/generated
-Iada -I../../gcc/ada -I../../gcc/ada/gcc-interface ../../gcc/ada/osint.adb -o
ada/osint.o

raised STORAGE_ERROR : stack overflow or erroneous memory access
make[3]: *** [../../gcc/ada/gcc-interface/Make-lang.in:119: ada/osint.o] Error
1