Linux 4.4.134-1-pve #1 SMP PVE 4.4.134-112 (Thu, 05 Jul 2018 12:39:16 +0000) x86_64 GNU/Linux

~/eoip# make
cc -c -o eoip.o eoip.c -O3 -Wall
eoip.c: In function ‘setprocname’:
eoip.c:8:3: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
for (int i = 0; environ[i]; i++) size += strlen(environ[i]) + 1;
^
eoip.c:8:3: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
eoip.c:11:12: error: redefinition of ‘i’
for (int i = 0; dst[i]; i++) size += strlen(dst[i]) + 1;
^
eoip.c:8:12: note: previous definition of ‘i’ was here
for (int i = 0; environ[i]; i++) size += strlen(environ[i]) + 1;
^
eoip.c:11:3: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
for (int i = 0; dst[i]; i++) size += strlen(dst[i]) + 1;
^
eoip.c: In function ‘main’:
eoip.c:38:3: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
for(int i = 1; i < argc; i++) {
^
Makefile:8: recipe for target 'eoip.o' failed
make: *** [eoip.o] Error 1