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From: degnbol@danbbs.dk To: gcc-gnats@gcc.gnu.org Subject: c/5929: gcc 2.95-3.04 miscompiles anonymous unions inside anonymous structs Date: Tue, 12 Mar 2002 15:06:00 -0000 [thread overview] Message-ID: <20020312225942.21817.qmail@sources.redhat.com> (raw) >Number: 5929 >Category: c >Synopsis: gcc 2.95-3.04 miscompiles anonymous unions inside anonymous structs >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Tue Mar 12 15:06:00 PST 2002 >Closed-Date: >Last-Modified: >Originator: Gunnar Degnbol >Release: Cygwin gcc 2.95-3, RH gcc 2.96.98, gcc 3.0.3, gcc 3.0.4 >Organization: >Environment: Cygwin/Windows NT4 (gcc 2.95-3) RH Linux 7.2 (gcc 3.0.3, gcc 3.0.4) >Description: The members of an anonymous union inside an anonymous struct are aligned with the first member of the anonymous struct. This affects Windows VARIANTs used in C programs. The bug does not affect C++ programs. >How-To-Repeat: $ gcc anonbug.c -o anonbug $ ./anonbug offset v1 = 0 offset v2 = 4 offset v3 = 8 offset u1 = 4 offset u2 = 4 $ g++ anonbug.c -o anonbug # or MS/Borland/intel C/C++ $ ./anonbug offset v1 = 0 offset v2 = 4 offset v3 = 8 offset u1 = 12 offset u2 = 12 >Fix: Not a fix but a workaround that works for me. A Windows VARIANT (Cygwin/Mingw32 oaidl.h, WINE oleauto.h) has this structure: struct tagVARIANT { union { struct { VARTYPE vt; // reserved fields union { // any kind of variable }; }; DECIMAL decVal; }; } VARIANT; Since nobody (?) actually uses decVal, a workaround for this specific instance is to #ifdef __cplusplus the outer anonymous union and struct. >Release-Note: >Audit-Trail: >Unformatted: ----gnatsweb-attachment---- Content-Type: application/octet-stream; name="anonbug.c" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="anonbug.c" I2lmZGVmIF9fY3BsdXNwbHVzDQpleHRlcm4gIkMiIHsNCiNlbmRpZg0KDQppbnQgcHJpbnRmKGNo YXIgKiwgLi4uKTsNCg0Kc3RydWN0IF9uZXN0ZWRhbm9uIHsNCiAgICBpbnQgdjE7DQogICAgc3Ry dWN0IHsNCiAgICAgICAgaW50IHYyOw0KICAgICAgICBpbnQgdjM7DQogICAgICAgIHVuaW9uIHsN CiAgICAgICAgICAgIGludCB1MTsNCiAgICAgICAgICAgIGludCB1MjsNCiAgICAgICAgfTsNCiAg ICB9Ow0KfTsNCg0KaW50IG1haW4oaW50IGFyZ2MsIGNoYXIgKiphcmd2KQ0Kew0KICAgIHN0cnVj dCBfbmVzdGVkYW5vbiBzOw0KICAgIHByaW50Zigib2Zmc2V0IHYxID0gJWRcbiIsIChpbnQpJnMu djEgLSAoaW50KSZzKTsNCiAgICBwcmludGYoIm9mZnNldCB2MiA9ICVkXG4iLCAoaW50KSZzLnYy IC0gKGludCkmcyk7DQogICAgcHJpbnRmKCJvZmZzZXQgdjMgPSAlZFxuIiwgKGludCkmcy52MyAt IChpbnQpJnMpOw0KICAgIHByaW50Zigib2Zmc2V0IHUxID0gJWRcbiIsIChpbnQpJnMudTEgLSAo aW50KSZzKTsNCiAgICBwcmludGYoIm9mZnNldCB1MiA9ICVkXG4iLCAoaW50KSZzLnUyIC0gKGlu dCkmcyk7DQp9DQoNCiNpZmRlZiBfX2NwbHVzcGx1cw0KfQ0KI2VuZGlmDQoNCg==
next reply other threads:[~2002-03-12 23:06 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-03-12 15:06 degnbol [this message] 2002-03-12 15:36 neil
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