Yes, function declarations did look like that. And GCC accepts it totally silently in pedantic ANSI C mode, not even warnings: 11:44:57 cory@tizona /home/

Yes, function declarations did look like that. And GCC accepts it totally silently in pedantic ANSI C mode, not even warnings: 11:44:57 cory@tizona /home/cory/Workspace/test $ cat knr.c #include <stdio.h> main(argc, argv) int argc; char **argv; { int z = foo(3, 4); printf("foo is %d\n", z); } foo(x, y) { return x + y; } 11:44:59 cory@tizona /home/cory/Workspace/test $ gcc -std=c89 -pedantic -o knr knr.c 11:45:07 cory@tizona /home/cory/Workspace/test $ ./knr foo is 7 11:45:11 cory@tizona /home/cory/Workspace/test $ gcc -v Reading specs from /usr/lib64/gcc/x86_64-slackware-linux/5.3.0/specs COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-slackware-linux/5.3.0/lto-wrapper Target: x86_64-slackware-linux Configured with: ../gcc-5.3.0/configure [...] Thread model: posix gcc version 5.3.0 (GCC) I seem to recall the compatibility was deliberate on the part of the ANSI C WG, for hopefully obvious reasons.