[pushed 0/9] analyzer: strlen, strcpy, and strcat [PR105899]

[David Malcolm <dmalcolm@redhat.com>]

This patch kit makes improvements to the analyzer's new strlen
implementation, and wires it up to strcpy and strcat.

For example, given:

  #include <string.h>

  void test (void)
  {
    char buf[10];
    strcpy (buf, "hello world!");
  }

we now emit:

demo.c: In function ‘test’:
demo.c:6:3: warning: stack-based buffer overflow [CWE-121] [-Wanalyzer-out-of-bounds]
    6 |   strcpy (buf, "hello world!");
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
  ‘test’: events 1-2
    |
    |    5 |   char buf[10];
    |      |        ^~~
    |      |        |
    |      |        (1) capacity: 10 bytes
    |    6 |   strcpy (buf, "hello world!");
    |      |   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    |      |   |
    |      |   (2) out-of-bounds write from byte 10 till byte 12 but ‘buf’ ends at byte 10
    |
demo.c:6:3: note: write of 3 bytes to beyond the end of ‘buf’
    6 |   strcpy (buf, "hello world!");
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
demo.c:6:3: note: valid subscripts for ‘buf’ are ‘[0]’ to ‘[9]’

  ┌─────┬─────┬────┬────┬────┬────┬────┬────┬────┬────┐┌─────┬─────┬─────┐
  │ [0] │ [1] │[2] │[3] │[4] │[5] │[6] │[7] │[8] │[9] ││[10] │[11] │[12] │
  ├─────┼─────┼────┼────┼────┼────┼────┼────┼────┼────┤├─────┼─────┼─────┤
  │ ‘h’ │ ‘e’ │‘l’ │‘l’ │‘o’ │‘ ’ │‘w’ │‘o’ │‘r’ │‘l’ ││ ‘d’ │ ‘!’ │ NUL │
  ├─────┴─────┴────┴────┴────┴────┴────┴────┴────┴────┴┴─────┴─────┴─────┤
  │                  string literal (type: ‘char[13]’)                   │
  └──────────────────────────────────────────────────────────────────────┘
     │     │    │    │    │    │    │    │    │    │      │     │     │
     │     │    │    │    │    │    │    │    │    │      │     │     │
     v     v    v    v    v    v    v    v    v    v      v     v     v
  ┌─────┬────────────────────────────────────────┬────┐┌─────────────────┐
  │ [0] │                  ...                   │[9] ││                 │
  ├─────┴────────────────────────────────────────┴────┤│after valid range│
  │             ‘buf’ (type: ‘char[10]’)              ││                 │
  └───────────────────────────────────────────────────┘└─────────────────┘
  ├─────────────────────────┬─────────────────────────┤├────────┬────────┤
                            │                                   │
                  ╭─────────┴────────╮              ╭───────────┴──────────╮
                  │capacity: 10 bytes│              │⚠️  overflow of 3 bytes│
                  ╰──────────────────╯              ╰──────────────────────╯

in addition to the pre-existing:

demo.c:6:3: warning: ‘__builtin_memcpy’ writing 13 bytes into a region of size 10 overflows the destination [-Wstringop-overflow=]
demo.c:5:8: note: destination object ‘buf’ of size 10
    5 |   char buf[10];
      |        ^~~

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
Pushed to trunk as r14-3461-g9aaec66917c96a through to
r14-3469-gbbdc0e0d0042ae.

David Malcolm (9):
  analyzer: add logging to impl_path_context
  analyzer: handle symbolic bindings in scan_for_null_terminator
    [PR105899]
  analyzer: reimplement kf_strcpy [PR105899]
  analyzer: eliminate region_model::get_string_size [PR105899]
  analyzer: reimplement kf_memcpy_memmove
  analyzer: handle strlen(INIT_VAL(STRING_REG)) [PR105899]
  analyzer: handle INIT_VAL(ELEMENT_REG(STRING_REG), CONSTANT_SVAL)
    [PR105899]
  analyzer: handle strlen(BITS_WITHIN) [PR105899]
  analyzer: implement kf_strcat [PR105899]

 gcc/analyzer/call-details.cc                  |  12 +-
 gcc/analyzer/call-details.h                   |   5 +-
 gcc/analyzer/engine.cc                        |  13 +-
 gcc/analyzer/kf.cc                            | 116 +++++---
 gcc/analyzer/region-model-manager.cc          |  19 ++
 gcc/analyzer/region-model.cc                  | 261 +++++++++++++-----
 gcc/analyzer/region-model.h                   |  22 +-
 gcc/doc/invoke.texi                           |   1 +
 .../analyzer/out-of-bounds-diagram-16.c       |  31 +++
 gcc/testsuite/gcc.dg/analyzer/sprintf-1.c     |  11 +
 gcc/testsuite/gcc.dg/analyzer/strcat-1.c      | 136 +++++++++
 gcc/testsuite/gcc.dg/analyzer/strcpy-1.c      |  22 ++
 gcc/testsuite/gcc.dg/analyzer/strcpy-3.c      |   8 +
 gcc/testsuite/gcc.dg/analyzer/strcpy-4.c      |  51 ++++
 14 files changed, 601 insertions(+), 107 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/analyzer/out-of-bounds-diagram-16.c
 create mode 100644 gcc/testsuite/gcc.dg/analyzer/strcat-1.c
 create mode 100644 gcc/testsuite/gcc.dg/analyzer/strcpy-4.c

-- 
2.26.3