portable way of getting EXEDIR

makefile

@@ -5,7 +5,7 @@ MANPREFIX = ${PREFIX}/share/man
 #CC ?= gcc
 SRCDIR = ./src
 CFLAGS = -Wall -Werror -pedantic -O3 -std=c11 -fno-strict-aliasing \
-	-I${SRCDIR} -I${PREFIX}/include/ -DLUA_USE_POSIX
+	-I${SRCDIR} -I${PREFIX}/include/ -DLUA_USE_POSIX -D_PREFIX="${PREFIX}"
 # remove this
 LDFLAGS = -L${PREFIX}/lib -lSDL2 -lm -llua5.2
 FILES != find ${SRCDIR} -name '*.c'

src/main.c

@@ -26,10 +26,16 @@ static double get_scale(void)
 
 static void get_exe_filename(char *buf, int sz)
 {
+#ifdef __linux__
 	char path[512];
 	sprintf(path, "/proc/%d/exe", getpid());
 	int len = readlink(path, buf, sz - 1);
 	buf[len] = '\0';
+#elif defined(_PREFIX)
+	strncpy(buf, _PREFIX, sz);
+#else
+	strncpy(buf, "/usr/local/share/lite/", sz);
+#endif
 }
 
 static void init_window_icon(void)