https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83011
--- Comment #2 from Julien ÉLIE <julien at trigofacile dot com> --- Created attachment 42644 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42644&action=edit Preprocessed translation unit of timer.c Thanks Martin for your response. I attached the result of the following command: /home/iulius/work/gcc/gcc-7.2.0/bin/gcc -g -O3 -DDEBUG=1 -Wall -Werror -Wextra -Wformat=2 -Wformat-overflow=2 -Wformat-truncation=2 -Wnull-dereference -Winit-self -Wmissing-include-dirs -Wshift-overflow=2 -Wsync-nand -Wstringop-overflow=4 -Wmissing-format-attribute -Walloc-zero -Walloca -Wduplicated-cond -Wtrampolines -Wshadow -Wpointer-arith -Wc99-c11-compat -Wbad-function-cast -Wcast-align -Wwrite-strings -Wdangling-else -Wdate-time -Wjump-misses-init -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-declarations -Wnormalized=nfc -Wrestrict -Wnested-externs -Winline -Winvalid-pch -Wvla -Wno-unused-function -I../include -E timer.c -fPIC -DPIC -o .libs/timer.o In English, the warning is: timer.c:395:37: error: ' ' directive output may be truncated writing 1 byte into a region of size between 0 and 1 [-Werror=format-truncation=] rc = snprintf(buf, len, "%s ", prefix); ~ timer.c:395:12: note: 'snprintf' output 2 or more bytes (assuming 3) into a destination of size 1 rc = snprintf(buf, len, "%s ", prefix); ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I'm not using -flto to build the projet. And, in case it could help, if I add "-flto" to compiler options, I no longer have the warning. Is it normal?
