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| author | Richard Biener <rguenther@suse.de> | 2022-05-25 11:49:03 +0200 |
|---|---|---|
| committer | Richard Biener <rguenther@suse.de> | 2022-05-27 11:42:31 +0200 |
| commit | e7c482b08076bb299742883c4ffd65b31e33200c (patch) | |
| tree | 976b5fa154ef456031e361eb4f0645d9c4050da9 | |
| parent | e2f014fcefcd2ad56b31995329820bbd99072eae (diff) | |
| download | gcc-e7c482b08076bb299742883c4ffd65b31e33200c.zip gcc-e7c482b08076bb299742883c4ffd65b31e33200c.tar.gz gcc-e7c482b08076bb299742883c4ffd65b31e33200c.tar.bz2 | |
tree-optimization/105726 - adjust array bound heuristic
There's heuristic to detect ptr[1].a[...] out of bound accesses
reasoning that if ptr points to an array of aggregates a trailing
incomplete array has to have size zero. The following more
thoroughly constrains the cases this applies to avoid false
positive diagnostics.
2022-05-25 Richard Biener <rguenther@suse.de>
PR tree-optimization/105726
* gimple-ssa-warn-restrict.cc (builtin_memref::set_base_and_offset):
Constrain array-of-flexarray case more.
* g++.dg/warn/Warray-bounds-27.C: New testcase.
| -rw-r--r-- | gcc/gimple-ssa-warn-restrict.cc | 22 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/warn/Warray-bounds-27.C | 16 |
2 files changed, 29 insertions, 9 deletions
diff --git a/gcc/gimple-ssa-warn-restrict.cc b/gcc/gimple-ssa-warn-restrict.cc index b678e80..734cdd7 100644 --- a/gcc/gimple-ssa-warn-restrict.cc +++ b/gcc/gimple-ssa-warn-restrict.cc @@ -525,7 +525,6 @@ builtin_memref::set_base_and_offset (tree expr) { tree memrefoff = fold_convert (ptrdiff_type_node, TREE_OPERAND (base, 1)); extend_offset_range (memrefoff); - base = TREE_OPERAND (base, 0); if (refoff != HOST_WIDE_INT_MIN && TREE_CODE (expr) == COMPONENT_REF) @@ -538,14 +537,19 @@ builtin_memref::set_base_and_offset (tree expr) REFOFF is set to s[1].b - (char*)s. */ offset_int off = tree_to_shwi (memrefoff); refoff += off; - } - - if (!integer_zerop (memrefoff)) - /* A non-zero offset into an array of struct with flexible array - members implies that the array is empty because there is no - way to initialize such a member when it belongs to an array. - This must be some sort of a bug. */ - refsize = 0; + + if (!integer_zerop (memrefoff) + && !COMPLETE_TYPE_P (TREE_TYPE (expr)) + && multiple_of_p (sizetype, memrefoff, + TYPE_SIZE_UNIT (TREE_TYPE (base)), true)) + /* A non-zero offset into an array of struct with flexible array + members implies that the array is empty because there is no + way to initialize such a member when it belongs to an array. + This must be some sort of a bug. */ + refsize = 0; + } + + base = TREE_OPERAND (base, 0); } if (TREE_CODE (ref) == COMPONENT_REF) diff --git a/gcc/testsuite/g++.dg/warn/Warray-bounds-27.C b/gcc/testsuite/g++.dg/warn/Warray-bounds-27.C new file mode 100644 index 0000000..06ce089 --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Warray-bounds-27.C @@ -0,0 +1,16 @@ +// PR105726 +// { dg-do compile } +// { dg-require-effective-target c++11 } +// { dg-options "-O2 -Warray-bounds" } + +#include <array> +#include <cstring> + +struct X { + char pad[4]; + std::array<char, 1> mField; +}; + +void encode(char* aBuffer, const X& aMessage) { + strncpy(aBuffer, aMessage.mField.data(), 1); // { dg-bogus "bounds" } +} |