From: Andrew Burgess <aburgess@redhat.com>
To: gdb-patches@sourceware.org
Subject: [PATCH 4/5] sim/erc32: avoid dereferencing type-punned pointer warnings
Date: Wed, 12 Oct 2022 13:38:34 +0100 [thread overview]
Message-ID: <b36f2b9339266fdef2e34970f932782925744ba4.1665578246.git.aburgess@redhat.com> (raw)
In-Reply-To: <cover.1665578246.git.aburgess@redhat.com>
When building the erc32 simulator I get a few warnings like this:
/tmp/build/sim/../../src/sim/erc32/exec.c:1377:21: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
1377 | sregs->fs[rd] = *((float32 *) & ddata[0]);
| ~^~~~~~~~~~~~~~~~~~~~~~~
The type of '& ddata[0]' will be 'uint32_t *', which is what triggers
the warning.
This commit uses an intermediate pointer of type 'char *' when
performing the type-punning, which is well-defined behaviour, and will
silence the above warning.
With this change, I now see no warnings when compiling exec.c, which
means that the line in Makefile.in that disables -Werror can be
removed.
There should be no change in behaviour after this commit.
---
sim/erc32/Makefile.in | 3 ---
sim/erc32/exec.c | 12 +++++++++---
2 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/sim/erc32/Makefile.in b/sim/erc32/Makefile.in
index 786ae1dcc7b..41830aab726 100644
--- a/sim/erc32/Makefile.in
+++ b/sim/erc32/Makefile.in
@@ -32,9 +32,6 @@ SIM_EXTRA_CLEAN = clean-sis
# behaviour of UART interrupt routines ...
SIM_EXTRA_CFLAGS += -DFAST_UART -I$(srcroot)
-# Some modules don't build cleanly yet.
-exec.o: SIM_WERROR_CFLAGS =
-
## COMMON_POST_CONFIG_FRAG
# `sis' doesn't need interf.o.
diff --git a/sim/erc32/exec.c b/sim/erc32/exec.c
index ef93692e7a2..af9ad9ea9ab 100644
--- a/sim/erc32/exec.c
+++ b/sim/erc32/exec.c
@@ -1345,7 +1345,8 @@ dispatch_instruction(struct pstate *sregs)
if (mexc) {
sregs->trap = TRAP_DEXC;
} else {
- sregs->fs[rd] = *((float32 *) & data);
+ char *ptr = (char *) &data;
+ sregs->fs[rd] = *((float32 *) ptr);
}
break;
case LDDF:
@@ -1371,13 +1372,18 @@ dispatch_instruction(struct pstate *sregs)
if (mexc) {
sregs->trap = TRAP_DEXC;
} else {
+ char *ptr;
+
rd &= 0x1E;
sregs->flrd = rd;
- sregs->fs[rd] = *((float32 *) & ddata[0]);
+
+ ptr = (char *) &ddata[0];
+ sregs->fs[rd] = *((float32 *) ptr);
#ifdef STAT
sregs->nload++; /* Double load counts twice */
#endif
- sregs->fs[rd + 1] = *((float32 *) & ddata[1]);
+ ptr = (char *) &ddata[1];
+ sregs->fs[rd + 1] = *((float32 *) ptr);
sregs->ltime = ebase.simtime + sregs->icnt + FLSTHOLD +
sregs->hold + sregs->fhold;
}
--
2.25.4
next prev parent reply other threads:[~2022-10-12 12:38 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-12 12:38 [PATCH 0/5] Silence some build warnings in various simulators Andrew Burgess
2022-10-12 12:38 ` [PATCH 1/5] sim/cgen: mask uninitialized variable warning in cgen-run.c Andrew Burgess
2022-10-23 12:30 ` Mike Frysinger
2022-10-24 15:57 ` Andrew Burgess
2022-10-24 15:59 ` Mike Frysinger
2022-10-27 15:53 ` Andrew Burgess
2022-10-12 12:38 ` [PATCH 2/5] sim/ppc: fix warnings related to printf format strings Andrew Burgess
2022-10-12 12:46 ` Tsukasa OI
2022-10-12 13:50 ` Andrew Burgess
2022-10-23 12:20 ` Mike Frysinger
2022-10-24 15:41 ` Andrew Burgess
2022-10-12 12:38 ` [PATCH 3/5] sim/ppc: mark device_error function as ATTRIBUTE_NORETURN Andrew Burgess
2022-10-12 12:38 ` Andrew Burgess [this message]
2022-10-12 14:11 ` [PATCH 4/5] sim/erc32: avoid dereferencing type-punned pointer warnings Pedro Alves
2022-10-12 17:02 ` Lancelot SIX
2022-10-13 10:35 ` Andrew Burgess
2022-10-13 10:49 ` Pedro Alves
2022-10-23 12:34 ` Mike Frysinger
2022-10-24 15:42 ` Andrew Burgess
2022-10-12 12:38 ` [PATCH 5/5] sim/iq2000: silence pointer-sign warnings Andrew Burgess
2022-10-23 12:32 ` Mike Frysinger
2022-10-24 15:45 ` Andrew Burgess
2022-10-26 8:51 ` Mike Frysinger
2022-10-14 17:50 ` [PATCH 0/5] Silence some build warnings in various simulators Tom Tromey
2022-10-19 13:34 ` Andrew Burgess
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