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* [Bug tree-optimization/92893] [10 Regression] Unhelpful -Wstringop-overflow warning for a trailing one-element array
[not found] <bug-92893-4@http.gcc.gnu.org/bugzilla/>
@ 2020-04-18 17:13 ` law at redhat dot com
2020-04-18 17:52 ` msebor at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 4+ messages in thread
From: law at redhat dot com @ 2020-04-18 17:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893
--- Comment #6 from Jeffrey A. Law <law at redhat dot com> ---
Isn't this ultimately a case of relying on the type information from that MEM
expression in a place where it's not valid?
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/92893] [10 Regression] Unhelpful -Wstringop-overflow warning for a trailing one-element array
[not found] <bug-92893-4@http.gcc.gnu.org/bugzilla/>
2020-04-18 17:13 ` [Bug tree-optimization/92893] [10 Regression] Unhelpful -Wstringop-overflow warning for a trailing one-element array law at redhat dot com
@ 2020-04-18 17:52 ` msebor at gcc dot gnu.org
2020-04-18 18:49 ` law at redhat dot com
2020-05-01 18:55 ` sbergman at redhat dot com
3 siblings, 0 replies; 4+ messages in thread
From: msebor at gcc dot gnu.org @ 2020-04-18 17:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893
--- Comment #7 from Martin Sebor <msebor at gcc dot gnu.org> ---
(In reply to Jeffrey A. Law from comment #6)
> Isn't this ultimately a case of relying on the type information from that
> MEM expression in a place where it's not valid?
Yes, as I mentioned in comment #1, it's by design (which could stand to
improve). I rewritten the whole function (compute_objsize) to deal with this
and a number of other problems due to the limitations of
compute_builtin_object_size (constant sizes, no ranges) that it relies on but
the changes are more intrusive than I feel comfortable for GCC 10.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/92893] [10 Regression] Unhelpful -Wstringop-overflow warning for a trailing one-element array
[not found] <bug-92893-4@http.gcc.gnu.org/bugzilla/>
2020-04-18 17:13 ` [Bug tree-optimization/92893] [10 Regression] Unhelpful -Wstringop-overflow warning for a trailing one-element array law at redhat dot com
2020-04-18 17:52 ` msebor at gcc dot gnu.org
@ 2020-04-18 18:49 ` law at redhat dot com
2020-05-01 18:55 ` sbergman at redhat dot com
3 siblings, 0 replies; 4+ messages in thread
From: law at redhat dot com @ 2020-04-18 18:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893
Jeffrey A. Law <law at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #8 from Jeffrey A. Law <law at redhat dot com> ---
Ultimately a duplicate of 87296. Both are using the type of &MEM_REF which
leads to the invalid diagnotics.
*** This bug has been marked as a duplicate of bug 87296 ***
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/92893] [10 Regression] Unhelpful -Wstringop-overflow warning for a trailing one-element array
[not found] <bug-92893-4@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2020-04-18 18:49 ` law at redhat dot com
@ 2020-05-01 18:55 ` sbergman at redhat dot com
3 siblings, 0 replies; 4+ messages in thread
From: sbergman at redhat dot com @ 2020-05-01 18:55 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92893
--- Comment #9 from Stephan Bergmann <sbergman at redhat dot com> ---
(In reply to Martin Sebor from comment #2)
> Defining Str like so works for the test case:
>
> struct Str {
> template<typename T1, typename T2> Str(Cat<T1, T2> c)
> {
> struct Flex { char c, a[]; } *p = (Flex*)get();
> c.add(p->a);
> }
> };
So I had created <https://gerrit.libreoffice.org/c/core/+/85161> "Silence bogus
-Wstringop-overflow with GCC trunk towards GCC 10" back in last December, and
it sufficed to suppress all those warnings when compiling LibreOffice with
then-trunk GCC, with optimizations enabled. However, meanwhile GCC has changed
again so that at least one place in the LibreOffice code now produces two
-Werror=stringop-overflow= in one such
struct Hack { char c; char a[]; };
workaround. (While in general the workarounds appear to still be effective in
suppressing other such warnings.) Bisecting, I found that first
> commit ef29b12cfbb4979a89b3cbadbf485a77c8fd8fce
> Author: Martin Sebor <msebor@redhat.com>
> Date: Sat Dec 14 00:52:46 2019 +0000
>
> PR middle-end/91582 - missing heap overflow detection for strcpy
caused a new "writing 1 byte into a region of size 0" at
> In file included from /home/user/libreoffice/include/rtl/string.hxx:41,
> from /home/user/libreoffice/include/rtl/ustring.hxx:37,
> from /home/user/libreoffice/include/unotest/filters-test.hxx:14,
> from /home/user/libreoffice/unotest/source/cpp/filters-test.cxx:14:
> In member function ‘char* rtl::OStringConcat<T1, T2>::addData(char*) const [with T1 = rtl::OStringLiteral; T2 = const char [2]]’,
> inlined from ‘char* rtl::OStringConcat<T1, T2>::addData(char*) const [with T1 = rtl::OStringConcat<rtl::OStringLiteral, const char [2]>; T2 = rtl::OString]’ at /home/user/libreoffice/include/rtl/stringconcat.hxx:256:114,
> inlined from ‘rtl::OString::OString(rtl::OStringConcat<T1, T2>&&) [with T1 = rtl::OStringConcat<rtl::OStringLiteral, const char [2]>; T2 = rtl::OString]’ at /home/user/libreoffice/include/rtl/string.hxx:281:34,
> inlined from ‘void test::FiltersTest::recursiveScan(test::filterStatus, const rtl::OUString&, const rtl::OUString&, const rtl::OUString&, SfxFilterFlags, SotClipboardFormatId, unsigned int, bool)’ at /home/user/libreoffice/unotest/source/cpp/filters-test.cxx:111:67:
> /home/user/libreoffice/include/rtl/stringconcat.hxx:77:11: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
> 77 | memcpy( buffer, data, length );
> | ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
> In file included from /home/user/libreoffice/include/rtl/ustring.hxx:37,
> from /home/user/libreoffice/include/unotest/filters-test.hxx:14,
> from /home/user/libreoffice/unotest/source/cpp/filters-test.cxx:14:
> /home/user/libreoffice/include/rtl/string.hxx: In member function ‘void test::FiltersTest::recursiveScan(test::filterStatus, const rtl::OUString&, const rtl::OUString&, const rtl::OUString&, SfxFilterFlags, SotClipboardFormatId, unsigned int, bool)’:
> /home/user/libreoffice/include/rtl/string.hxx:280:32: note: at offset 0 to object ‘rtl::OString::OString(rtl::OStringConcat<T1, T2>&&) [with T1 = rtl::OStringConcat<rtl::OStringLiteral, const char [2]>; T2 = rtl::OString]::Hack::c’ with size 1 declared here
> 280 | struct Hack { char c; char a[]; };
> | ^
and later
> commit a9a437ffc4269650e34af92c4fb095b7ed98f94a
> Author: Jakub Jelinek <jakub@redhat.com>
> Date: Tue Mar 17 13:36:41 2020 +0100
>
> tree-ssa-strlen: Fix up count_nonzero_bytes* [PR94015]
started to even cause an additional "writing 4 bytes into a region of size 1"
> In file included from /home/user/libreoffice/include/rtl/string.hxx:41,
> from /home/user/libreoffice/include/rtl/ustring.hxx:37,
> from /home/user/libreoffice/include/unotest/filters-test.hxx:14,
> from /home/user/libreoffice/unotest/source/cpp/filters-test.cxx:14:
> In function ‘char* rtl::addDataHelper(char*, const char*, std::size_t)’,
> inlined from ‘static char* rtl::ToStringHelper<rtl::OStringLiteral>::addData(char*, const rtl::OStringLiteral&)’ at /home/user/libreoffice/include/rtl/string.hxx:1907:91,
> inlined from ‘char* rtl::OStringConcat<T1, T2>::addData(char*) const [with T1 = rtl::OStringLiteral; T2 = const char [2]]’ at /home/user/libreoffice/include/rtl/stringconcat.hxx:222:103,
> inlined from ‘char* rtl::OStringConcat<T1, T2>::addData(char*) const [with T1 = rtl::OStringConcat<rtl::OStringLiteral, const char [2]>; T2 = rtl::OString]’ at /home/user/libreoffice/include/rtl/stringconcat.hxx:256:114,
> inlined from ‘rtl::OString::OString(rtl::OStringConcat<T1, T2>&&) [with T1 = rtl::OStringConcat<rtl::OStringLiteral, const char [2]>; T2 = rtl::OString]’ at /home/user/libreoffice/include/rtl/string.hxx:281:34,
> inlined from ‘void test::FiltersTest::recursiveScan(test::filterStatus, const rtl::OUString&, const rtl::OUString&, const rtl::OUString&, SfxFilterFlags, SotClipboardFormatId, unsigned int, bool)’ at /home/user/libreoffice/unotest/source/cpp/filters-test.cxx:111:67:
> /home/user/libreoffice/include/rtl/stringconcat.hxx:77:11: error: writing 4 bytes into a region of size 1 [-Werror=stringop-overflow=]
> 77 | memcpy( buffer, data, length );
> | ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
> In file included from /home/user/libreoffice/include/rtl/ustring.hxx:37,
> from /home/user/libreoffice/include/unotest/filters-test.hxx:14,
> from /home/user/libreoffice/unotest/source/cpp/filters-test.cxx:14:
> /home/user/libreoffice/include/rtl/string.hxx: In member function ‘void test::FiltersTest::recursiveScan(test::filterStatus, const rtl::OUString&, const rtl::OUString&, const rtl::OUString&, SfxFilterFlags, SotClipboardFormatId, unsigned int, bool)’:
> /home/user/libreoffice/include/rtl/string.hxx:280:32: note: at offset 0 to object ‘rtl::OString::OString(rtl::OStringConcat<T1, T2>&&) [with T1 = rtl::OStringConcat<rtl::OStringLiteral, const char [2]>; T2 = rtl::OString]::Hack::c’ with size 1 declared here
> 280 | struct Hack { char c; char a[]; };
> | ^
preceding the other warning.
^ permalink raw reply [flat|nested] 4+ messages in thread
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[not found] <bug-92893-4@http.gcc.gnu.org/bugzilla/>
2020-04-18 17:13 ` [Bug tree-optimization/92893] [10 Regression] Unhelpful -Wstringop-overflow warning for a trailing one-element array law at redhat dot com
2020-04-18 17:52 ` msebor at gcc dot gnu.org
2020-04-18 18:49 ` law at redhat dot com
2020-05-01 18:55 ` sbergman at redhat dot com
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