working on "duff" example led me to futzing with gdb, found out the gdb tutorial is kinda (a lot) outdated

.gitignore

@@ -1,3 +1,4 @@
 gowrikumar/bin
+gdbtut/bin
 *.i
 *.s

Makefile

@@ -2,16 +2,18 @@ CD = cd
 RM = rm -v
 
 CC := gcc
-CFLAGS := -std=c99 -Wall
+CFLAGS := -std=c99 -Wall -g
 
 export CD RM CFLAGS
 
 
 all:
 	$(CD) gowrikumar && $(MAKE)
+	$(CD) gdbtut && $(MAKE)
 
 clean:
 	$(CD) gowrikumar && $(MAKE) clean
+	$(CD) gdbtut && $(MAKE) clean
 
 
 .PHONY: all clean

gdbtut/Makefile

@@ -0,0 +1,14 @@
+# tutorial exercises from http://www.unknownroad.com/rtfm/gdbtut/
+
+BINDIR := $(PWD)/bin
+export BINDIR
+
+
+all:
+	$(CD) src && $(MAKE)
+
+clean:
+	$(RM) $(BINDIR)/*
+
+
+.PHONY: all clean

gdbtut/src/Makefile

@@ -0,0 +1,12 @@
+# tutorial exercises from http://www.unknownroad.com/rtfm/gdbtut/
+
+ALL_BIN := $(patsubst %.c,$(BINDIR)/%,$(wildcard *.c))
+
+
+$(BINDIR)/%: %.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+all: $(ALL_BIN)
+
+
+.PHONY: all

gdbtut/src/segfault.c

@@ -0,0 +1,28 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char **argv)
+{
+    char *buf;
+    long long huge = 8000000000000000000;
+    /* Okay, so this is *not* going to segfault because
+     * the way memory is allocated has changed since
+     * the tutorial was written.  The segfault is supposed
+     * to happen when more memory is allocated than is
+     * available on the machine.  So much for that exercise.
+     */
+
+    buf = malloc(huge);
+
+    fgets(buf, 1024, stdin);
+    printf("%s\n", buf);
+
+    return 1;
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

gowrikumar/src/11-duff.c

@@ -0,0 +1,37 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+void duff(register char *to, register char *from, register int count)
+{
+    register int n = (count + 7) / 8;
+    switch (count % 8) {
+        case 0: do { *to++ = *from++;
+        case 7: *to++ = *from++;
+        case 6: *to++ = *from++;
+        case 5: *to++ = *from++;
+        case 4: *to++ = *from++;
+        case 3: *to++ = *from++;
+        case 2: *to++ = *from++;
+        case 1: *to++ = *from++;
+        } while (--n > 0);
+    }
+}
+
+int main()
+{
+    char * to = "dogs cats babies";
+    char * from = "monkey hat pants";
+    int i = 16;
+    printf("to = %s\n", to);
+    printf("from = %s\n", from);
+    /* And here comes the segfault... */
+    duff(to, from, i);
+    printf("to = %s\n", to);
+    printf("from = %s\n", from);
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */

gowrikumar/src/11b-duff.c

@@ -0,0 +1,40 @@
+/**
+ * :author: Dan Buch (daniel.buch@gmail.com)
+ */
+
+#include <stdio.h>
+
+void duff(register char *to, register char *from, register int count)
+{
+    register int n;
+
+    int remainder = count % 8;
+    if (remainder == 0) {
+        n = (count + 7) / 8;
+        do {
+            *to++ = *from++;
+        } while (--n > 0);
+    } else if (remainder <= 7 && remainder > 0) {
+        int i;
+        int c;
+        for (i = 0; (c = from[i] && c != EOF); i++) {
+            to[i] = c;
+        }
+    }
+}
+
+int main()
+{
+    char * to = "dogs cats babies";
+    char * from = "monkey hat pants";
+    int i = 11;
+    printf("to = %s\n", to);
+    printf("from = %s\n", from);
+    /* And here comes the segfault... */
+    duff(to, from, i);
+    printf("to = %s\n", to);
+    printf("from = %s\n", from);
+}
+
+/* vim:filetype=c:fileencoding=utf-8
+ */