Permit re-setting --object-bits

Support choosing the number of object bits to be used by CBMC at runtime
even with pre-compiled goto binaries. Update the goto-cc section in the
CPROVER manual to remove any documentation of object-bits (it remains
documented in the "Memory and pointers in CBMC" section).

Fixes: diffblue#5443

Author: tautschnig

doc/cprover-manual/goto-cc.md

@@ -132,9 +132,6 @@ most important architectural parameters are:
     `sizeof(long int)` on various machines.
 -   The width of pointers; for example, compare the value of `sizeof(int *)` on
     various machines.
--   The number of bits in a pointer which are used to differentiate between
-    different objects. The remaining bits of a pointer are used for offsets
-    within objects.
 -   The [endianness](http://en.wikipedia.org/wiki/Endianness) of
     the architecture.
 
@@ -152,8 +149,6 @@ following command-line arguments can be passed to the CPROVER tools:
 -   The word-width can be set with `--16`, `--32`, `--64`.
 -   The endianness can be defined with `--little-endian` and
     `--big-endian`.
--   The number of bits in a pointer used to differentiate between different
-    objects can be set using `--object-bits x`. Where `x` is the number of bits.
 
 When using a goto binary, CBMC and the other tools read the
 configuration from the binary. The setting when running goto-cc is

doc/man/goto-cc.1

@@ -96,9 +96,10 @@ files.
 .TP
 \fB\-\-print\-rejected\-preprocessed\-source\fR \fIfile\fR
 Copy failing (preprocessed) source to \fIfile\fR.
-.TP
-\fB\-\-object\-bits\fR \fIN\fR
-Configure the number of bits used for object numbering in CBMC's pointer encoding.
+.SH BACKWARD COMPATIBILITY
+.B goto\-cc
+will warn and ignore the use of \fB\-\-object\-bits\fR, which previous versions
+processed. This option now instead needs to be passed to \fBcbmc\fR(1).
 .SH ENVIRONMENT
 All tools honor the TMPDIR environment variable when generating temporary
 files and directories.

regression/CMakeLists.txt

@@ -63,7 +63,6 @@ else()
   add_subdirectory(goto-cl)
 endif()
 add_subdirectory(goto-cc-cbmc)
-add_subdirectory(goto-cc-cbmc-shared-options)
 add_subdirectory(cbmc-cpp)
 add_subdirectory(goto-cc-goto-analyzer)
 add_subdirectory(goto-analyzer-simplify)

regression/Makefile

@@ -36,7 +36,6 @@ DIRS = cbmc-shadow-memory \
        goto-gcc \
        goto-cl \
        goto-cc-cbmc \
-       goto-cc-cbmc-shared-options \
        cbmc-cpp \
        goto-cc-goto-analyzer \
        goto-analyzer-simplify \

regression/cbmc/simplify_singleton_interval_7690/singleton_interval_in_assume_7690.c

@@ -5,8 +5,6 @@
 #include <stdlib.h>
 #include <stdint.h>
 
-extern size_t __CPROVER_max_malloc_size;
-
 #if defined(_WIN32) && defined(_M_X64)
 int __builtin_clzll(unsigned long long);
 #define __nof_symex_objects                                                    \

regression/goto-cc-cbmc-shared-options/CMakeLists.txt

@@ -1,4 +1,4 @@
-CORE winbug
+CORE
 test.c
 --function main --object-bits 6
 ^EXIT=10$

regression/goto-cc-cbmc-shared-options/Makefile

@@ -1,4 +1,4 @@
-CORE winbug
+CORE
 test.c
 --function main --object-bits 10
 ^EXIT=10$

regression/goto-cc-cbmc-shared-options/README.md

@@ -130,34 +130,6 @@ static std::string architecture_string(T value, const char *s)
          std::string(s) + "=" + std::to_string(value) + ";\n";
 }
 
-/// The maximum allocation size is determined by the number of bits that
-/// are left in the pointer of width \p pointer_width.
-///
-/// The allocation size cannot exceed the number represented by the (signed)
-/// offset, otherwise it would not be possible to store a pointer into a
-/// valid bit of memory. Therefore, the max allocation size is
-/// 2^(offset_bits - 1), where the offset bits is the number of bits left in the
-/// pointer after the object bits.
-///
-/// The offset must be signed, as a pointer can point to the end of the memory
-/// block, and needs to be able to point back to the start.
-/// \param pointer_width: The width of the pointer
-/// \param object_bits : The number of bits used to represent the ID
-/// \return The size in bytes of the maximum allocation supported.
-static mp_integer
-max_malloc_size(std::size_t pointer_width, std::size_t object_bits)
-{
-  PRECONDITION(pointer_width >= 1);
-  PRECONDITION(object_bits < pointer_width);
-  PRECONDITION(object_bits >= 1);
-  const auto offset_bits = pointer_width - object_bits;
-  // We require the offset to be able to express upto allocation_size - 1,
-  // but also down to -allocation_size, therefore the size is allowable
-  // is number of bits, less the signed bit.
-  const auto bits_for_positive_offset = offset_bits - 1;
-  return ((mp_integer)1) << (mp_integer)bits_for_positive_offset;
-}
-
 void ansi_c_internal_additions(std::string &code)
 {
   // clang-format off
@@ -181,9 +153,9 @@ void ansi_c_internal_additions(std::string &code)
       CPROVER_PREFIX "size_t size, " CPROVER_PREFIX "bool zero);\n"
     "void " CPROVER_PREFIX "deallocate(void *);\n"
 
-    CPROVER_PREFIX "size_t " CPROVER_PREFIX "max_malloc_size="+
-    integer2string(max_malloc_size(config.ansi_c.pointer_width, config
-    .bv_encoding.object_bits));
+    CPROVER_PREFIX "thread_local " CPROVER_PREFIX "size_t "
+      CPROVER_PREFIX "max_malloc_size="+
+      integer2string(config.max_malloc_size());
   if(config.ansi_c.pointer_width==config.ansi_c.long_int_width)
     code += "UL;\n";
   else if(config.ansi_c.pointer_width==config.ansi_c.long_long_int_width)

regression/goto-cc-cbmc-shared-options/chain.sh

@@ -52,4 +52,5 @@ void cprover_c_library_factory_force_load(
   const std::set<irep_idt> &functions,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler);
+
 #endif // CPROVER_ANSI_C_CPROVER_LIBRARY_H

regression/goto-cc-cbmc-shared-options/object-bits/default_bits.desc renamed to regression/goto-cc-cbmc/object-bits/default_bits.desc

@@ -26,8 +26,11 @@ extern const void *__CPROVER_deallocated;
 extern const void *__CPROVER_memory_leak;
 
 extern int __CPROVER_malloc_failure_mode;
-extern __CPROVER_size_t __CPROVER_max_malloc_size;
 extern __CPROVER_bool __CPROVER_malloc_may_fail;
+// The maximum size of an object that we can handle under the object:offset
+// pointer encoding. Marked thread-local as it is a per-analysis constant that
+// can safely be constant-propagated even in concurrent execution.
+extern __CPROVER_thread_local __CPROVER_size_t __CPROVER_max_malloc_size;
 
 // malloc failure modes
 extern int __CPROVER_malloc_failure_mode_return_null;

regression/goto-cc-cbmc-shared-options/object-bits/fewer_bits.desc renamed to regression/goto-cc-cbmc/object-bits/fewer_bits.desc

@@ -7,7 +7,6 @@
 #define __CPROVER_contracts_library_defined
 
 // external dependencies
-extern __CPROVER_size_t __CPROVER_max_malloc_size;
 const void *__CPROVER_alloca_object = 0;
 extern const void *__CPROVER_deallocated;
 const void *__CPROVER_new_object = 0;

regression/goto-cc-cbmc-shared-options/object-bits/more_bits.desc renamed to regression/goto-cc-cbmc/object-bits/more_bits.desc

@@ -770,6 +770,8 @@ int cbmc_parse_optionst::get_goto_program(
 
   goto_model = initialize_goto_model(cmdline.args, ui_message_handler, options);
 
+  update_max_malloc_size(goto_model, ui_message_handler);
+
   if(cmdline.isset("show-symbol-table"))
   {
     show_symbol_table(goto_model, ui_message_handler);

regression/goto-cc-cbmc-shared-options/object-bits/test.c renamed to regression/goto-cc-cbmc/object-bits/test.c

@@ -29,7 +29,6 @@ const char *goto_cc_options_with_separated_argument[]=
   "--native-linker",
   "--print-rejected-preprocessed-source",
   "--mangle-suffix",
-  "--object-bits",
   nullptr
 };
 

src/ansi-c/ansi_c_internal_additions.cpp

@@ -74,7 +74,6 @@ void goto_cc_modet::help()
     "symbols\n"
     " {y--print-rejected-preprocessed-source} {ufile} \t "
     "copy failing (preprocessed) source to file\n"
-    " {y--object-bits} {N} \t number of bits used for object addresses\n"
     "\n");
 }
 

src/ansi-c/cprover_library.h

@@ -11,6 +11,8 @@ Author: Daniel Kroening, [email protected]
 
 #include "initialize_goto_model.h"
 
+#include <util/arith_tools.h>
+#include <util/c_types.h>
 #include <util/config.h>
 #include <util/exception_utils.h>
 #include <util/message.h>
@@ -22,6 +24,7 @@ Author: Daniel Kroening, [email protected]
 #include <langapi/language.h>
 #include <langapi/language_file.h>
 #include <langapi/mode.h>
+#include <linking/static_lifetime_init.h>
 
 #include "goto_convert_functions.h"
 #include "read_goto_binary.h"
@@ -236,3 +239,29 @@ goto_modelt initialize_goto_model(
 
   return goto_model;
 }
+
+void update_max_malloc_size(
+  goto_modelt &goto_model,
+  message_handlert &message_handler)
+{
+  if(!goto_model.symbol_table.has_symbol(CPROVER_PREFIX "max_malloc_size"))
+    return;
+
+  const auto previous_max_malloc_size_value = numeric_cast<mp_integer>(
+    goto_model.symbol_table.lookup_ref(CPROVER_PREFIX "max_malloc_size").value);
+  const mp_integer current_max_malloc_size = config.max_malloc_size();
+
+  if(
+    !previous_max_malloc_size_value.has_value() ||
+    *previous_max_malloc_size_value != current_max_malloc_size)
+  {
+    symbolt &max_malloc_size_sym = goto_model.symbol_table.get_writeable_ref(
+      CPROVER_PREFIX "max_malloc_size");
+    max_malloc_size_sym.value =
+      from_integer(current_max_malloc_size, size_type());
+    max_malloc_size_sym.value.set(ID_C_no_nondet_initialization, true);
+
+    if(goto_model.can_produce_function(INITIALIZE_FUNCTION))
+      recreate_initialize_function(goto_model, message_handler);
+  }
+}

src/ansi-c/library/cprover.h

@@ -56,4 +56,8 @@ void set_up_custom_entry_point(
   bool try_mode_lookup,
   message_handlert &message_handler);
 
+/// Update the initial value of `__CPROVER_max_malloc_size` in case the number
+/// of object bits has changed.
+void update_max_malloc_size(goto_modelt &, message_handlert &);
+
 #endif // CPROVER_GOTO_PROGRAMS_INITIALIZE_GOTO_MODEL_H

src/ansi-c/library/cprover_contracts.c

@@ -13,6 +13,7 @@ Author: Qinheping Hu
 #include <util/unicode.h>
 #include <util/version.h>
 
+#include <goto-programs/initialize_goto_model.h>
 #include <goto-programs/read_goto_binary.h>
 #include <goto-programs/set_properties.h>
 #include <goto-programs/show_goto_functions.h>
@@ -73,6 +74,8 @@ int goto_synthesizer_parse_optionst::doit()
     configure_gcc(gcc_version);
   }
 
+  update_max_malloc_size(goto_model, ui_message_handler);
+
   // Get options for the backend verifier and preprocess `goto_model`.
   const auto &options = get_options();
 

src/cbmc/cbmc_parse_options.cpp

@@ -1468,3 +1468,28 @@ irep_idt configt::this_operating_system()
 
   return this_os;
 }
+
+/// The maximum allocation size is determined by the number of bits that
+/// are left in the pointer of width `ansi_c.pointer_width`.
+///
+/// The allocation size cannot exceed the number represented by the (signed)
+/// offset, otherwise it would not be possible to store a pointer into a
+/// valid bit of memory. Therefore, the max allocation size is
+/// 2^(offset_bits - 1), where the offset bits is the number of bits left in the
+/// pointer after the object bits.
+///
+/// The offset must be signed, as a pointer can point to the end of the memory
+/// block, and needs to be able to point back to the start.
+/// \return The size in bytes of the maximum allocation supported.
+mp_integer configt::max_malloc_size() const
+{
+  PRECONDITION(ansi_c.pointer_width >= 1);
+  PRECONDITION(bv_encoding.object_bits < ansi_c.pointer_width);
+  PRECONDITION(bv_encoding.object_bits >= 1);
+  const auto offset_bits = ansi_c.pointer_width - bv_encoding.object_bits;
+  // We require the offset to be able to express upto allocation_size - 1,
+  // but also down to -allocation_size, therefore the size is allowable
+  // is number of bits, less the signed bit.
+  const auto bits_for_positive_offset = offset_bits - 1;
+  return ((mp_integer)1) << (mp_integer)bits_for_positive_offset;
+}

src/goto-cc/gcc_cmdline.cpp

@@ -358,6 +358,7 @@ class configt
 
   void set_object_bits_from_symbol_table(const symbol_table_baset &);
   std::string object_bits_info();
+  mp_integer max_malloc_size() const;
 
   static irep_idt this_architecture();
   static irep_idt this_operating_system();

src/goto-cc/goto_cc_mode.cpp

@@ -49,7 +49,6 @@ SRC += analyses/ai/ai.cpp \
        analyses/variable-sensitivity/variable_sensitivity_domain/to_predicate.cpp \
        analyses/variable-sensitivity/variable_sensitivity_test_helpers.cpp \
        ansi-c/expr2c.cpp \
-       ansi-c/max_malloc_size.cpp \
        ansi-c/type2name.cpp \
        ansi-c/c_typecheck_base.cpp \
        big-int/big-int.cpp \
@@ -168,6 +167,7 @@ SRC += analyses/ai/ai.cpp \
        util/json_object.cpp \
        util/lazy.cpp \
        util/lower_byte_operators.cpp \
+       util/max_malloc_size.cpp \
        util/memory_info.cpp \
        util/message.cpp \
        util/optional_utils.cpp \