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memcheck: make --partial-loads-ok=yes work again, but now make it

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the non-default (it's a hack after all).


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@5035
This commit is contained in:
Julian Seward 2005-11-08 02:25:37 +00:00
parent 7d716ad8ce
commit 7f31b1528f
3 changed files with 37 additions and 16 deletions
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27
memcheck/docs/mc-manual.xml
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@ -46,9 +46,6 @@ Memcheck can detect the following problems:</para>
<computeroutput>memcpy()</computeroutput> and related
functions</para>
</listitem>
<listitem>
<para>Some misuses of the POSIX pthreads API</para>
</listitem>
</itemizedlist>
</sect1>
@ -159,19 +156,25 @@ Memcheck can detect the following problems:</para>
<listitem id="partial">
<para><computeroutput>--partial-loads-ok=yes</computeroutput>
[default]</para>
<para><computeroutput>--partial-loads-ok=no</computeroutput></para>
<para>Controls how Memcheck handles word (4-byte) loads from
</para>
<para><computeroutput>--partial-loads-ok=no</computeroutput>[default]
</para>
<para>Controls how Memcheck handles word-sized, word-aligned loads from
addresses for which some bytes are addressible and others are
not. When <computeroutput>yes</computeroutput> (the
default), such loads do not elicit an address error.
not. When <computeroutput>yes</computeroutput>,
such loads do not elicit an address error.
Instead, the loaded V bytes corresponding to the illegal
addresses indicate undefined, and those corresponding to
addresses indicate Undefined, and those corresponding to
legal addresses are loaded from shadow memory, as usual.</para>
<para>When <computeroutput>no</computeroutput>, loads from
partially invalid addresses are treated the same as loads
from completely invalid addresses: an illegal-address error
<para>When <computeroutput>no</computeroutput>(the default),
loads from partially invalid addresses are treated the same as
loads from completely invalid addresses: an illegal-address error
is issued, and the resulting V bytes indicate valid data.</para>
<para>Note that code that behaves in this way is in violation of
the the ISO C/C++ standards, and should be considered broken.
If at all possible, such code should be fixed. This flag should
be used only as a last resort.
</para>
</listitem>
<listitem id="strlen">

4
memcheck/mac_shared.c
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@ -58,7 +58,7 @@
/*--- Command line options ---*/
/*------------------------------------------------------------*/
Bool MAC_(clo_partial_loads_ok) = True;
Bool MAC_(clo_partial_loads_ok) = False;
Int MAC_(clo_freelist_vol) = 5000000;
LeakCheckMode MAC_(clo_leak_check) = LC_Summary;
VgRes MAC_(clo_leak_resolution) = Vg_LowRes;
@ -100,7 +100,7 @@ void MAC_(print_common_usage)(void)
" --leak-check=no|summary|full search for memory leaks at exit? [summary]\n"
" --leak-resolution=low|med|high how much bt merging in leak check [low]\n"
" --show-reachable=no|yes show reachable blocks in leak check? [no]\n"
" --partial-loads-ok=no|yes too hard to explain here; see manual [yes]\n"
" --partial-loads-ok=no|yes too hard to explain here; see manual [no]\n"
" --freelist-vol=<number> volume of freed blocks queue [5000000]\n"
" --workaround-gcc296-bugs=no|yes self explanatory [no]\n"
);

22
memcheck/mc_main.c
View File

@ -417,7 +417,7 @@ ULong mc_LOADVn_slow ( Addr a, SizeT szB, Bool bigendian )
SizeT i = szB-1;
SizeT n_addrs_bad = 0;
Addr ai;
Bool aok;
Bool aok, partial_load_exemption_applies;
UWord abit, vbyte;
PROF_EVENT(30, "mc_LOADVn_slow");
@ -436,7 +436,25 @@ ULong mc_LOADVn_slow ( Addr a, SizeT szB, Bool bigendian )
i--;
}
if (n_addrs_bad > 0)
/* This is a hack which avoids producing errors for code which
insists in stepping along byte strings in aligned word-sized
chunks, and there is a partially defined word at the end. (eg,
optimised strlen). Such code is basically broken at least WRT
semantics of ANSI C, but sometimes users don't have the option
to fix it, and so this option is provided. Note it is now
defaulted to not-engaged.
A load from a partially-addressible place is allowed if:
- the command-line flag is set
- it's a word-sized, word-aligned load
- at least one of the addresses in the word *is* valid
*/
partial_load_exemption_applies
= MAC_(clo_partial_loads_ok) && szB == VG_WORDSIZE
&& VG_IS_WORD_ALIGNED(a)
&& n_addrs_bad < VG_WORDSIZE;
if (n_addrs_bad > 0 && !partial_load_exemption_applies)
MAC_(record_address_error)( VG_(get_running_tid)(), a, szB, False );
return vw;