Adding tests for function pointer removal

These tests demonstrate the different ways in which we could easily do
better in function pointer resolution. At the moment, each example
thinks the function pointer could be any of the 9 functions but in all
cases can do much better (either know exactly the function or subset of
functions)

Added const to arrays that aren't modified which will then be used to
determine arrays whose contents can be known.

Added test for arrays that are not constant and are in fact
modified.

Adding test for when FP array declared as a pointer

The function pointer optimsation can be further improved by dealing
with things like structs and pointers to function pointers. More
detail is outlined in diffblue#476

Added test for nullptr terminated arrays

Adding const struct regression tests

FPs may not always be assigned into a const FP and instead may be called
in place (e.g. directly from the array). This modifies the exprt
structure that must be unpacked. These tests demonstrate the different
ways that can be done.

Adding and correcting tests for pointers to FPs

Author: thk123

regression/goto-analyzer/fp-removal1/main.c

@@ -0,0 +1,27 @@
+#include <stdio.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+void func()
+{
+  const void_fp fp = f2;
+  fp();
+}
+
+void main(){
+  func();
+}

regression/goto-analyzer/fp-removal1/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.c
+--show-goto-functions
+
+^Removing function pointers and virtual functions$
+^\s*f2();
+--
+^warning: ignoring

regression/goto-analyzer/fp-removal10/main.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+void_fp fp_tbl[] = {f2, f3, f4};
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+void func(void_fp fp, int i){
+  fp_tbl[2] = fp;
+  const void_fp fp2 = fp_tbl[2];
+  fp2();
+}
+
+void main(){
+   for(int i=0;i<3;i++){
+     func(fp_all[i+3], i);
+   }
+}

regression/goto-analyzer/fp-removal10/test.desc

@@ -0,0 +1,17 @@
+CORE
+main.c
+--show-goto-functions
+
+^Removing function pointers and virtual functions$
+^\s*IF fp2 == f1 THEN GOTO 1$
+^\s*IF fp2 == f2 THEN GOTO 2$
+^\s*IF fp2 == f3 THEN GOTO 3$
+^\s*IF fp2 == f4 THEN GOTO 4$
+^\s*IF fp2 == f5 THEN GOTO 5$
+^\s*IF fp2 == f6 THEN GOTO 6$
+^\s*IF fp2 == f7 THEN GOTO 7$
+^\s*IF fp2 == f8 THEN GOTO 8$
+^\s*IF fp2 == f9 THEN GOTO 9$
+^SIGNAL=0$
+--
+^warning: ignoring

regression/goto-analyzer/fp-removal11/main.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+void func(){
+  void_fp * const fp_tbl= malloc(sizeof(void_fp) * 3);
+  fp_tbl[0]=f2;
+  fp_tbl[1]=f3;
+  fp_tbl[2]=f4;
+  const void_fp fp = fp_tbl[1];
+  fp();
+}
+
+void main(){
+  func();
+}

regression/goto-analyzer/fp-removal11/test.desc

@@ -0,0 +1,17 @@
+CORE
+main.c
+--show-goto-functions
+
+^Removing function pointers and virtual functions$
+^\s*IF fp == f1 THEN GOTO 1$
+^\s*IF fp == f2 THEN GOTO 2$
+^\s*IF fp == f3 THEN GOTO 3$
+^\s*IF fp == f4 THEN GOTO 4$
+^\s*IF fp == f5 THEN GOTO 5$
+^\s*IF fp == f6 THEN GOTO 6$
+^\s*IF fp == f7 THEN GOTO 7$
+^\s*IF fp == f8 THEN GOTO 8$
+^\s*IF fp == f9 THEN GOTO 9$
+^SIGNAL=0$
+--
+^warning: ignoring

regression/goto-analyzer/fp-removal12/main.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+typedef struct fp_container
+{
+  const void_fp fp_tbl[3];
+} fp_container;
+
+
+
+void func(){
+  fp_container container = { .fp_tbl = {f2 ,f3, f4} };
+  fp_container container2 = { .fp_tbl = {f5 ,f6, f7} };
+  // Illegal:
+  // container = container2;
+  const void_fp fp = container.fp_tbl[1];
+  fp();
+}
+
+void main(){
+  func();
+}

regression/goto-analyzer/fp-removal12/test.desc

@@ -0,0 +1,15 @@
+KNOWNBUG
+main.c
+--show-goto-functions
+
+^Removing function pointers and virtual functions$
+^\s*f3();$
+^SIGNAL=0$
+--
+^warning: ignoring
+--
+This test is marked as a KNOWNBUG as it is possible for the function
+pointer to be optimized away. Currently goto-analyzer falls back to
+assuming it could be any type compatible function.
+
+Issue: https://github.com/diffblue/cbmc/issues/476

regression/goto-analyzer/fp-removal13/main.c

@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+typedef struct fp_container
+{
+  void_fp fp_tbl[3];
+} fp_container;
+
+
+
+void func(){
+  const fp_container container = { .fp_tbl = {f2 ,f3, f4} };
+  fp_container container2 = { .fp_tbl = {f5 ,f6, f7} };
+  const void_fp alternatate_fp_tbl[] = {f5 ,f6, f7};
+  // Illegal:
+  // container = container2;
+  // container.fp_tbl = alternatate_fp_tbl;
+  // container.fp_tbl[1] = f4;
+  const void_fp fp = container.fp_tbl[1];
+  fp();
+}
+
+void main(){
+  func();
+}

regression/goto-analyzer/fp-removal13/test.desc

@@ -0,0 +1,15 @@
+CORE
+main.c
+--show-goto-functions --verbosity 10
+
+^Removing function pointers and virtual functions$
+^\s*f3();$
+^SIGNAL=0$
+--
+^warning: ignoring
+--
+This test is marked as a KNOWNBUG as it is possible for the function
+pointer to be optimized away. Currently goto-analyzer falls back to
+assuming it could be any type compatible function.
+
+Issue: https://github.com/diffblue/cbmc/issues/476

regression/goto-analyzer/fp-removal14/main.c

@@ -0,0 +1,32 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+void func(){
+  const void_fp fp = f3;
+  const void_fp fp2 = f4;
+  const void_fp* const p2fp = &fp;
+  // Illegal:
+  //p2fp = &fp2;
+  //fp = f5;
+  (*p2fp)();
+}
+
+void main(){
+  func();
+}

regression/goto-analyzer/fp-removal14/test.desc

@@ -0,0 +1,15 @@
+KNOWNBUG
+main.c
+--show-goto-functions
+
+^Removing function pointers and virtual functions$
+^\s*f3();$
+^SIGNAL=0$
+--
+^warning: ignoring
+--
+This test is marked as a KNOWNBUG as it is possible for the function
+pointer to be optimized away. Currently goto-analyzer falls back to
+assuming it could be any type compatible function.
+
+Issue: https://github.com/diffblue/cbmc/issues/476

regression/goto-analyzer/fp-removal15/main.c

@@ -0,0 +1,28 @@
+#include <stdio.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+void func()
+{
+  void_fp fp = f2;
+  fp = f3;
+  fp();
+}
+
+void main(){
+  func();
+}

regression/goto-analyzer/fp-removal15/test.desc

@@ -0,0 +1,17 @@
+CORE
+main.c
+--show-goto-functions
+
+^Removing function pointers and virtual functions$
+^\s*IF fp == f1 THEN GOTO 1$
+^\s*IF fp == f2 THEN GOTO 2$
+^\s*IF fp == f3 THEN GOTO 3$
+^\s*IF fp == f4 THEN GOTO 4$
+^\s*IF fp == f5 THEN GOTO 5$
+^\s*IF fp == f6 THEN GOTO 6$
+^\s*IF fp == f7 THEN GOTO 7$
+^\s*IF fp == f8 THEN GOTO 8$
+^\s*IF fp == f9 THEN GOTO 9$
+^SIGNAL=0$
+--
+^warning: ignoring

regression/goto-analyzer/fp-removal16/main.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+
+void f1 (void) { printf("%i", 1); }
+void f2 (void) { printf("%i", 2); }
+void f3 (void) { printf("%i", 3); }
+void f4 (void) { printf("%i", 4); }
+void f5 (void) { printf("%i", 5); }
+void f6 (void) { printf("%i", 6); }
+void f7 (void) { printf("%i", 7); }
+void f8 (void) { printf("%i", 8); }
+void f9 (void) { printf("%i", 9); }
+
+typedef void(*void_fp)(void);
+
+// There is a basic check that excludes all functions that aren't used anywhere
+// This ensures that check can't work in this example
+const void_fp fp_all[] = {f1, f2 ,f3, f4, f5 ,f6, f7, f8, f9};
+
+void func()
+{
+  const void_fp fp = f2;
+  const void_fp fp3 = f4;
+  void_fp fp2 = fp;
+  fp2 = fp3;
+  fp2();
+}
+
+void main()
+{
+  func();
+}

regression/goto-analyzer/fp-removal16/test.desc

@@ -0,0 +1,16 @@
+CORE
+main.c
+--show-goto-functions
+^Removing function pointers and virtual functions$
+^\s*IF fp2 == f1 THEN GOTO 1$
+^\s*IF fp2 == f2 THEN GOTO 2$
+^\s*IF fp2 == f3 THEN GOTO 3$
+^\s*IF fp2 == f4 THEN GOTO 4$
+^\s*IF fp2 == f5 THEN GOTO 5$
+^\s*IF fp2 == f6 THEN GOTO 6$
+^\s*IF fp2 == f7 THEN GOTO 7$
+^\s*IF fp2 == f8 THEN GOTO 8$
+^\s*IF fp2 == f9 THEN GOTO 9$
+^SIGNAL=0$
+--
+^warning: ignoring