Hello,
I am using valgrind-3.6.0.SVN-Debian, and cant work out why I am getting
Invalid read errors.
The routine is one which is adding symbols to a std::map, indexed by
their virtual address. As multiple symbols may share the same virtual
address, I need to concatenate the symbol names in the already present
symbol entry.
I have the following (cut down, debugging) code which demonstrates the
problem:
Symbol * prev = prev_itt->second;
char * prev_name = prev->name;
size_t newsize = strlen(prev_name);
newsize += strlen(sym->name);
newsize += 2;
prev->name = new char[newsize];
//Should concat and delete prev_name, but for debugging
leave like this
delete [] prev->name;
//For debugging, put this back, so no leaks
prev->name = prev_name;
With the new char[newsize] and delete [] prev->name commented out,
valgrind is perfectly happy with the code (which is effectively a nop)
However, with the new and delete present as above, valigrind complains with:
==10046== Invalid read of size 1
==10046== at 0x4C286E4: __GI_strlen (mc_replace_strmem.c:284)
==10046== by 0x40CB88: SymbolTable::insert(Symbol*) (symbol-table.cpp:37)
==10046== by 0x406536: parse_symbol_file(std::string) (main.cpp:44)
==10046== by 0x406DA4: main (main.cpp:70)
==10046== Address 0x7ae7d36 is 0 bytes after a block of size 6 alloc'd
==10046== at 0x4C27939: operator new[](unsigned long)
(vg_replace_malloc.c:305)
==10046== by 0x40C969: Symbol::Symbol(unsigned long long, char, char
const*) (symbol.cpp:9)
==10046== by 0x406526: parse_symbol_file(std::string) (main.cpp:44)
==10046== by 0x406DA4: main (main.cpp:70)
==10046==
==10046== Invalid read of size 1
==10046== at 0x4C286E4: __GI_strlen (mc_replace_strmem.c:284)
==10046== by 0x40CB94: SymbolTable::insert(Symbol*) (symbol-table.cpp:38)
==10046== by 0x406536: parse_symbol_file(std::string) (main.cpp:44)
==10046== by 0x406DA4: main (main.cpp:70)
==10046== Address 0x7ae7fe6 is 0 bytes after a block of size 6 alloc'd
==10046== at 0x4C27939: operator new[](unsigned long)
(vg_replace_malloc.c:305)
==10046== by 0x40C969: Symbol::Symbol(unsigned long long, char, char
const*) (symbol.cpp:9)
==10046== by 0x406526: parse_symbol_file(std::string) (main.cpp:44)
==10046== by 0x406DA4: main (main.cpp:70)
Where the two errors are referring to the two strlen() calls when
calculating newsize.
Are these errors indicating a supposed bug in my code, or are they
complaining about something in the __GI_strlen replaced code. If so,
does this mean there is a bug in __GI_strlen ?
Thanks in advance,
--
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com
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