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From: jason@cambridge.redhat.com To: gcc-gnats@gcc.gnu.org Subject: middle-end/6950: gcc 3.0.4 miscompiles cppexp.c Date: Thu, 06 Jun 2002 16:56:00 -0000 [thread overview] Message-ID: <20020606235219.183D5F8D1D@prospero.cambridge.redhat.com> (raw) >Number: 6950 >Category: middle-end >Synopsis: gcc 3.0.4 miscompiles cppexp.c >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Thu Jun 06 16:56:01 PDT 2002 >Closed-Date: >Last-Modified: >Originator: Jason Merrill >Release: 3.0.4 >Organization: Red Hat, Inc. >Environment: System: Linux prospero.cambridge.redhat.com 2.4.9-31 #1 Tue Feb 26 07:11:02 EST 2002 i686 unknown Architecture: i686 host: i686-pc-linux-gnu build: i686-pc-linux-gnu target: i686-pc-linux-gnu configured with: /home/jason/eg/configure --with-gcc-version-trigger=/home/jason/eg/gcc/version.c --host=i686-pc-linux-gnu -v --with-dwarf2 --enable-threads=posix --with-as=/home/jason/s/sw/gas/as-new --with-ld=/home/jason/s/sw/ld/ld-new : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) : (reconfigured) >Description: In Neil's recent changes to cppexp.c, num_equality_op stores the result of a && expression into a location which is used in the expression. gcc 3.0.4 wrongly generates code for this which first stores 0 into the target, then computes the expression, to poor result. This bug is not present in 2.95.3, Red Hat 2.96-98 or 3.1.0. I plan to work around this bug in the trunk sources, but it might still be a good idea to fix this in a 3.0.5 release. >How-To-Repeat: Here is a reduced testcase. typedef struct cpp_num cpp_num; struct cpp_num { long high; long low; char overflow; }; #define num_eq(num1, num2) (num1.low == num2.low && num1.high == num2.high) static cpp_num num_equality_op (lhs, rhs) cpp_num lhs, rhs; { lhs.low = num_eq (lhs, rhs); lhs.high = 0; lhs.overflow = 0; return lhs; } int main() { cpp_num a = { 1, 2 }; cpp_num b = { 3, 4 }; cpp_num result = num_equality_op (a, b); if (result.low) return 1; result = num_equality_op (a, a); if (!result.low) return 2; return 0; } >Fix: >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2002-06-06 23:56 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-06-06 16:56 jason [this message] 2002-12-03 14:50 bangerth 2002-12-03 22:46 Jason Merrill 2002-12-04 6:26 bangerth
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