Commit Graph

8 Commits

Author SHA1 Message Date
Roman Lebedev 6de129e710 [Sema] Re-land: Diagnose tautological comparison with type's min/max values
The first attempt, rL315614 was reverted because one libcxx
test broke, and i did not know at the time how to deal with it.

Summary:
Currently, clang only diagnoses completely out-of-range comparisons (e.g. `char` and constant `300`),
and comparisons of unsigned and `0`. But gcc also does diagnose the comparisons with the
`std::numeric_limits<>::max()` / `std::numeric_limits<>::min()` so to speak

Finally Fixes https://bugs.llvm.org/show_bug.cgi?id=34147
Continuation of https://reviews.llvm.org/D37565

Reviewers: rjmccall, rsmith, aaron.ballman

Reviewed By: rsmith

Subscribers: rtrieu, jroelofs, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D38101

llvm-svn: 315875
2017-10-15 20:13:17 +00:00
Roman Lebedev 6f405dbe5c Revert "[Sema] Diagnose tautological comparison with type's min/max values"
This reverts r315614,r315615,r315621,r315622
Breaks http://bb9.pgr.jp/#/builders/20/builds/59

/home/bb9/bootstrap-clang-libcxx-lld-i686-linux/llvm-project/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp:95:17: error: comparison 'long long' > 9223372036854775807 is always false [-Werror,-Wtautological-constant-compare]
    if (max_sec > Lim::max()) return false;
        ~~~~~~~ ^ ~~~~~~~~~~
/home/bb9/bootstrap-clang-libcxx-lld-i686-linux/llvm-project/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp:124:13: error: comparison 'long long' < -9223372036854775808 is always false [-Werror,-Wtautological-constant-compare]
    if (sec < Lim::min() || sec > Lim::max())   return false;
        ~~~ ^ ~~~~~~~~~~
/home/bb9/bootstrap-clang-libcxx-lld-i686-linux/llvm-project/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp:124:33: error: comparison 'long long' > 9223372036854775807 is always false [-Werror,-Wtautological-constant-compare]
    if (sec < Lim::min() || sec > Lim::max())   return false;
                            ~~~ ^ ~~~~~~~~~~
3 errors generated.
--

I'm not yet sure what is the proper fix.

llvm-svn: 315631
2017-10-12 22:03:20 +00:00
Roman Lebedev bd1fc22043 [Sema] Diagnose tautological comparison with type's min/max values
Summary:
Currently, clang only diagnoses completely out-of-range comparisons (e.g. `char` and constant `300`),
and comparisons of unsigned and `0`. But gcc also does diagnose the comparisons with the
`std::numeric_limits<>::max()` / `std::numeric_limits<>::min()` so to speak

Finally Fixes https://bugs.llvm.org/show_bug.cgi?id=34147
Continuation of https://reviews.llvm.org/D37565

Reviewers: rjmccall, rsmith, aaron.ballman

Reviewed By: rsmith

Subscribers: rtrieu, jroelofs, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D38101

llvm-svn: 315614
2017-10-12 20:16:51 +00:00
Roman Lebedev 6aa34aadd1 [Sema] -Wtautological-compare: handle comparison of unsigned with 0S.
Summary:
This is a first half(?) of a fix for the following bug:
https://bugs.llvm.org/show_bug.cgi?id=34147 (gcc -Wtype-limits)

GCC's -Wtype-limits does warn on comparison of unsigned value
with signed zero (as in, with 0), but clang only warns if the
zero is unsigned (i.e. 0U).

Also, be careful not to double-warn, or falsely warn on
comparison of signed/fp variable and signed 0.

Yes, all these testcases are needed.

Testing: $ ninja check-clang-sema check-clang-semacxx
Also, no new warnings for clang stage-2 build.

Reviewers: rjmccall, rsmith, aaron.ballman

Reviewed By: rjmccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D37565

llvm-svn: 312750
2017-09-07 22:14:25 +00:00
David Majnemer 6a42665f9f Revert "Properly consider the range of enum for range comparisons in C mode"
The approach r183084 took was wrong, back it out.

llvm-svn: 183575
2013-06-07 22:07:20 +00:00
David Majnemer 3fbb763a92 Properly consider the range of enum for range comparisons in C mode
In some cases, clang applies the C++ rules for computing the range of a
value when said value is an enum.

Instead, apply C semantics when in C mode.

llvm-svn: 183084
2013-06-02 08:11:22 +00:00
Fariborz Jahanian 2f4e33aba2 Improvements to my patch in r164143 per
Richard's comments. // rdar://12202422

llvm-svn: 164316
2012-09-20 19:36:41 +00:00
Fariborz Jahanian b1885425c4 c: warn when an integer value comparison with an
integral expression have the obvious result.
Patch reviewed by John McCall off line.
// rdar://12202422

llvm-svn: 164143
2012-09-18 17:37:21 +00:00