This patch adds the "shrinks buffer" case to the success_with_move
modelling of realloc.
Regression-tested on Linux x86-64, further ran the analyzer tests with
the -m32 option.
2022-08-11 Tim Lange <m...@tim-lange.me>
gcc/analyzer/ChangeLog:
PR analyzer/106539
* region-model-impl-calls.cc (region_model::impl_call_realloc):
Use the result of get_copied_size as the size for the
sized_regions in realloc.
(success_with_move::get_copied_size): New function.
gcc/testsuite/ChangeLog:
PR analyzer/106539
* gcc.dg/analyzer/pr106539.c: New test.
* gcc.dg/analyzer/realloc-5.c: New test.
---
gcc/analyzer/region-model-impl-calls.cc | 48 ++++++++++++++++++++---
gcc/testsuite/gcc.dg/analyzer/pr106539.c | 15 +++++++
gcc/testsuite/gcc.dg/analyzer/realloc-5.c | 45 +++++++++++++++++++++
3 files changed, 102 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/analyzer/pr106539.c
create mode 100644 gcc/testsuite/gcc.dg/analyzer/realloc-5.c
diff --git a/gcc/analyzer/region-model-impl-calls.cc
b/gcc/analyzer/region-model-impl-calls.cc
index 8c38e9206fa..fa0ec88b1f4 100644
--- a/gcc/analyzer/region-model-impl-calls.cc
+++ b/gcc/analyzer/region-model-impl-calls.cc
@@ -732,15 +732,17 @@ region_model::impl_call_realloc (const call_details &cd)
const svalue *old_size_sval = model->get_dynamic_extents (freed_reg);
if (old_size_sval)
{
- const region *sized_old_reg
+ const svalue *copied_size_sval
+ = get_copied_size (old_size_sval, new_size_sval);
+ const region *copied_old_reg
= model->m_mgr->get_sized_region (freed_reg, NULL,
- old_size_sval);
+ copied_size_sval);
const svalue *buffer_content_sval
- = model->get_store_value (sized_old_reg, cd.get_ctxt ());
- const region *sized_new_reg
+ = model->get_store_value (copied_old_reg, cd.get_ctxt ());
+ const region *copied_new_reg
= model->m_mgr->get_sized_region (new_reg, NULL,
- old_size_sval);
- model->set_value (sized_new_reg, buffer_content_sval,
+ copied_size_sval);
+ model->set_value (copied_new_reg, buffer_content_sval,
cd.get_ctxt ());
}
else
@@ -774,6 +776,40 @@ region_model::impl_call_realloc (const call_details &cd)
else
return true;
}
+
+ private:
+ /* Return the lesser of OLD_SIZE_SVAL and NEW_SIZE_SVAL.
+ If either one is symbolic, the symbolic svalue is returned. */
+ const svalue *get_copied_size (const svalue *old_size_sval,
+ const svalue *new_size_sval) const
+ {
+ tree old_size_cst = old_size_sval->maybe_get_constant ();
+ tree new_size_cst = new_size_sval->maybe_get_constant ();
+
+ if (old_size_cst && new_size_cst)
+ {
+ /* Both are constants and comparable. */
+ tree cmp = fold_binary (LT_EXPR, boolean_type_node,
+ old_size_cst, new_size_cst);
+
+ if (cmp == boolean_true_node)
+ return old_size_sval;
+ else
+ return new_size_sval;
+ }
+ else if (new_size_cst)
+ {
+ /* OLD_SIZE_SVAL is symbolic, so return that. */
+ return old_size_sval;
+ }
+ else
+ {
+ /* NEW_SIZE_SVAL is symbolic or both are symbolic.
+ Return NEW_SIZE_SVAL, because implementations of realloc
+ probably only moves the buffer if the new size is larger. */
+ return new_size_sval;
+ }
+ }
};
/* Body of region_model::impl_call_realloc. */
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr106539.c
b/gcc/testsuite/gcc.dg/analyzer/pr106539.c
new file mode 100644
index 00000000000..fd270868e36
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr106539.c
@@ -0,0 +1,15 @@
+#include <stdlib.h>
+
+void *test (void)
+{
+ void **p = (void **)malloc (sizeof (void *) * 2);
+ if (!p)
+ return NULL;
+ p[0] = malloc(10);
+ p[1] = malloc(20); /* { dg-message "allocated here" } */
+ void *q = realloc (p, sizeof (void *)); /* { dg-message "when 'realloc'
succeeds, moving buffer" } */
+ if (!q)
+ /* { dg-warning "leak of '<unknown>'" "leak of unknown" { target *-*-* } .-1
} */
+ return p;
+ return q;
+}
diff --git a/gcc/testsuite/gcc.dg/analyzer/realloc-5.c
b/gcc/testsuite/gcc.dg/analyzer/realloc-5.c
new file mode 100644
index 00000000000..2efe3371e12
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/realloc-5.c
@@ -0,0 +1,45 @@
+#include "analyzer-decls.h"
+
+typedef __SIZE_TYPE__ size_t;
+
+#define NULL ((void *)0)
+
+extern void *malloc (size_t __size)
+ __attribute__ ((__nothrow__ , __leaf__))
+ __attribute__ ((__malloc__))
+ __attribute__ ((__alloc_size__ (1)));
+extern void *realloc (void *__ptr, size_t __size)
+ __attribute__ ((__nothrow__ , __leaf__))
+ __attribute__ ((__warn_unused_result__))
+ __attribute__ ((__alloc_size__ (2)));
+extern void free (void *__ptr)
+ __attribute__ ((__nothrow__ , __leaf__));
+extern void *memset (void *__ptr, int __value, size_t __size);
+
+/* realloc where the region shrinks on success_with_move. */
+
+void test_1 ()
+{
+ char *p = malloc (16);
+ if (!p)
+ return;
+ memset (p, 1, 16);
+
+ char *q = realloc (p, 8);
+ if (!q)
+ {
+ free (p);
+ return;
+ }
+ else if (p != q)
+ {
+ __analyzer_dump_capacity (q); /* { dg-warning "capacity:
'\\(\[^\n\r\]*\\)8'" } */
+ __analyzer_eval (q[8] == 1); /* { dg-line eval } */
+
+ /* { dg-warning "UNKNOWN" "warning" { target *-*-* } eval } */
+ /* { dg-warning "overread" "warning" { target *-*-* } eval } */
+ /* { dg-warning "use of uninitialized value" "warning" { target *-*-* }
eval } */
+ }
+
+ free (q);
+}
--
2.37.1
