wilfred:unix> gmake
gcc -I. -I../py -Wall -Werror -ansi -std=gnu99 -Os -DUSE_READLINE  -c -o build/main.o main.c
In file included from main.c:4:
/usr/include/malloc.h:4:2: error: #warning "<malloc.h> is obsolete, use <stdlib.h>"
Makefile:73: recipe for target 'build/main.o' failed
gmake: *** [build/main.o] Error 1
'''

Indeed, using stdlib.h silences this.