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Jakub Jelinek ca6c722561 c++: Handle COMPOUND_EXPRs in get_narrower and warnings_for_convert_and_check [PR91993]
As the testcases shows, the -Wconversion warning behaves quite differently
when -fsanitize=undefined vs. when not sanitizing, but in the end it is
not something specific to sanitizing, if a user uses
  return static_cast<uc>(static_cast<uc>((d++, a) << 1U) | b) | c;
instead of
  return static_cast<uc>(static_cast<uc>(a << 1U) | b) | c;
and thus there is some COMPOUND_EXPR involved, cp_build_binary_op behaves
significantly different, e.g. shorten_binary_op will have different result
(uc for the case without COMPOUND_EXPR, int with it), but it isn't limited
to that.

> How about improving get_narrower to handle COMPOUND_EXPR?  I'd think that
> would do the trick without affecting evaluation order.

Not completely, had to change also warnings_for_convert_and_check, but with
that it works.  The float-cast-overflow* changes are needed because now with
-O1+ we emit lots of -Woverflow warnings on the testcase, but we do emit
those warnings on the testcase even when compiling just with -O1 and without
-fsanitize=float-cast-overflow, so it seems to me a change in the right
direction, having -fsanitize= or explicit comma expressions smaller effect
on the warnings that are emitted.

2020-03-23  Jakub Jelinek  <jakub@redhat.com>

	PR c++/91993
	* tree.c (get_narrower): Handle COMPOUND_EXPR by recursing on
	ultimate rhs and if returned something different, reconstructing
	the COMPOUND_EXPRs.

	* c-warn.c (warnings_for_convert_and_check): For expr and/or
	result being COMPOUND_EXPRs, skip to ultimate rhs.

	* g++.dg/warn/Wconversion-pr91993.C: New test.
	* g++.dg/ubsan/pr91993.C: New test.
	* c-c++-common/ubsan/float-cast-overflow-1.c: Add -Wno-overflow
	to dg-options.
	* c-c++-common/ubsan/float-cast-overflow-2.c: Likewise.
	* c-c++-common/ubsan/float-cast-overflow-4.c: Likewise.
2020-03-23 19:47:24 +01:00
config Use a non-empty test program to test ability to link. 2020-02-12 13:22:07 -08:00
contrib contrib: Change 'remote' for personal branches and add branch creation script 2020-01-24 14:38:16 +00:00
fixincludes Allow CONFIG_SHELL to override build-time shell in mkheaders 2020-02-20 22:09:03 -03:00
gcc c++: Handle COMPOUND_EXPRs in get_narrower and warnings_for_convert_and_check [PR91993] 2020-03-23 19:47:24 +01:00
gnattools PR81878: fix --disable-bootstrap --enable-languages=ada 2018-11-20 00:07:47 +00:00
gotools libgo: update to Go1.14beta1 2020-01-21 23:53:22 -08:00
include Fix comma at end of enumerator list seen with -std=c++98. 2020-03-21 08:09:02 +01:00
INSTALL
intl Fixes after recent configure changes relating to static libraries 2020-02-01 00:34:28 +00:00
libada Add `--with-toolexeclibdir=' configuration option 2020-01-24 11:24:25 +00:00
libatomic libatomic: Fix last change [PR55930] 2020-02-22 19:55:09 +01:00
libbacktrace libbacktrace: update to current libgo test file 2020-02-15 18:25:13 -08:00
libcc1 c++: Fix return type deduction with an abbreviated function template 2020-02-10 20:43:53 -05:00
libcpp Update cpplib da.po. 2020-03-10 00:13:42 +00:00
libdecnumber Update copyright years. 2020-01-01 12:51:42 +01:00
libffi Add `--with-toolexeclibdir=' configuration option 2020-01-24 11:24:25 +00:00
libgcc [GCC][PATCH][ARM] Add multilib mapping for Armv8.1-M+MVE with -mfloat-abi=hard 2020-03-17 12:44:46 +00:00
libgfortran Use au->lock exclusively for locking in async I/O. 2020-02-18 19:45:25 +01:00
libgo runtime: handle linux/arm64 signal register 2020-02-28 12:24:21 -08:00
libgomp libgomp – fix declare target link handling (PR94251) 2020-03-23 15:29:05 +01:00
libhsail-rt Add `--with-toolexeclibdir=' configuration option 2020-01-24 11:24:25 +00:00
libiberty Keep .GCC.command.line sections of LTO objetcs 2020-03-05 08:44:11 +01:00
libitm Use a non-empty test program to test ability to link. 2020-02-12 13:22:07 -08:00
libobjc Use a non-empty test program to test ability to link. 2020-02-12 13:22:07 -08:00
liboffloadmic Add `--with-toolexeclibdir=' configuration option 2020-01-24 11:24:25 +00:00
libphobos libphobos: Reset libtool_VERSION to 1:0:0 2020-03-16 17:04:18 +01:00
libquadmath Use a non-empty test program to test ability to link. 2020-02-12 13:22:07 -08:00
libsanitizer Darwin, libsanitizer: Adjust minimum supported Darwin version (PR93731). 2020-03-01 14:40:57 +00:00
libssp Use a non-empty test program to test ability to link. 2020-02-12 13:22:07 -08:00
libstdc++-v3 libstdc++: Fix experimental::path::generic_string (PR 93245) 2020-03-21 22:11:44 +00:00
libvtv Add `--with-toolexeclibdir=' configuration option 2020-01-24 11:24:25 +00:00
lto-plugin API extension for binutils (type of symbols). 2020-03-19 16:56:27 +01:00
maintainer-scripts maintainer-scripts: Fix up gcc_release without -l, where mkdir was using umask 077 after migration 2020-03-12 18:30:16 +01:00
zlib Add `--with-toolexeclibdir=' configuration option 2020-01-24 11:24:25 +00:00
.dir-locals.el
.gitattributes Add *.md diff=md. 2020-01-15 14:29:53 +01:00
.gitignore Add .clangd and compile_commands.json to .gitignore. 2019-08-28 19:33:28 +00:00
ABOUT-NLS
ar-lib Update GCC to autoconf 2.69, automake 1.15.1 (PR bootstrap/82856). 2018-10-31 17:03:16 +00:00
ChangeLog configure - build libgomp by default for amdgcn 2020-03-09 17:00:39 +01:00
ChangeLog.jit
ChangeLog.tree-ssa
compile
config-ml.in MSP430: Add -fno-exceptions multilib 2019-12-11 19:19:50 +00:00
config.guess Update config.sub and config.guess. 2019-09-09 11:14:32 +02:00
config.rpath
config.sub Update config.sub and config.guess. 2019-09-09 11:14:32 +02:00
configure configure - build libgomp by default for amdgcn 2020-03-09 17:00:39 +01:00
configure.ac configure - build libgomp by default for amdgcn 2020-03-09 17:00:39 +01:00
COPYING
COPYING.LIB
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depcomp
install-sh
libtool-ldflags
libtool.m4 [ARM/FDPIC v6 02/24] [ARM] FDPIC: Handle arm*-*-uclinuxfdpiceabi in configure scripts 2019-09-10 09:37:00 +02:00
ltgcc.m4
ltmain.sh
ltoptions.m4
ltsugar.m4
ltversion.m4
lt~obsolete.m4
MAINTAINERS Update myself to MAINTAINERS 2020-03-11 23:32:40 -04:00
Makefile.def Sync top-level change from gdb 2019-06-15 21:32:03 +00:00
Makefile.in Makefile.tpl (HOST_EXPORTS): Add CXX_FOR_BUILD. 2019-08-23 15:37:22 -06:00
Makefile.tpl Makefile.tpl (HOST_EXPORTS): Add CXX_FOR_BUILD. 2019-08-23 15:37:22 -06:00
missing
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multilib.am Update GCC to autoconf 2.69, automake 1.15.1 (PR bootstrap/82856). 2018-10-31 17:03:16 +00:00
README
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test-driver Update GCC to autoconf 2.69, automake 1.15.1 (PR bootstrap/82856). 2018-10-31 17:03:16 +00:00
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