Hi Chiaki,
If you use --track-origins=yes, then valgrind will report where the variable
was first allocated (or put on the stack).
That's usually enough to figure out which it is.
][ Maurice van Swaaij, Blue Sky Studios ][
----- Original Message -----
| From: "chiaki ISHIKAWA" <ishik...@yk.rim.or.jp>
| To: valgrind-users@lists.sourceforge.net
| Sent: Thursday, April 23, 2015 12:13:38 PM
| Subject: [Valgrind-users] Can valgrind print the used "uninitialized
| value" and its size?
| Hi,
| I was running mozilla TB and found a message during a test run
| ==20163== Conditional jump or move depends on uninitialised value(s)
| ==20163== at 0x90974BC: nsJSObjWrapper::NP_SetProperty(NPObject*,
| void*, _NPVariant const*) (nsJSNPRuntime.cpp:137)
| ...
| so there is an uninitialized usage.
| In this particular instance, I realized that it would be really great
| to know the value of this uninitialized memory (turns out to be
| automatic variable on the stack.)
| so that I can learn what has happened to the subsequent processing.
| Can the uninitialized value was zero or not, for example?
| Can valgrind print value of used uninitialized memory location, say,
| something along the suggested manner below?
| I use the above example:
| ==20163== Conditional jump or move depends on uninitialised value(s)
| ==20163== The value used was: 0xdeadbeaf (4 bytes)
| ==20163== at 0x90974BC: nsJSObjWrapper::NP_SetProperty(NPObject*,
| void*, _NPVariant const*) (nsJSNPRuntime.cpp:137)
| ...
| or maybe considering the possibility of byte block:
| ==20163== Conditional jump or move depends on uninitialised value(s)
| ==20163== The value used started with 0xde 0xad 0xbe 0xaf 0xaa 0xbb
| 0xcc ... (up to the minimum of first N octets or the size of the
| data,
| maybe N can be 16 , etc.)
| ==20163== at 0x90974BC: nsJSObjWrapper::NP_SetProperty(NPObject*,
| void*, _NPVariant const*) (nsJSNPRuntime.cpp:137)
| I believe this simple addition makes the detection very useful
| because it would make creating the suggested patch easier by knowing
| why a program that has been used so long had a hidden issue for so
| many
| years.
| Thank you for sharing this great tool with the programming community.
| Best Regards,
| Chiaki Ishikawa
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