Valgrind 3.3 - Advanced Debugging and Profiling for GNU/Linux applications by J. Seward, N. Nethercote, J. Weidendorfer and the Valgrind Development Team Paperback (6"x9"), 164 pages ISBN 0954612051 RRP £12.95 ($19.95) Get a printed copy>>>

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5.6 Client Requests

The following client requests are defined in ‘memcheck.h’. See ‘memcheck.h’ for exact details of their arguments.

• VALGRIND_MAKE_MEM_NOACCESS, VALGRIND_MAKE_MEM_UNDEFINED and VALGRIND_MAKE_MEM_DEFINED. These mark address ranges as completely inaccessible, accessible but containing undefined data, and accessible and containing defined data, respectively. Subsequent errors may have their faulting addresses described in terms of these blocks. Returns a “block handle”. Returns zero when not run on Valgrind.
• VALGRIND_MAKE_MEM_DEFINED_IF_ADDRESSABLE. This is just like VALGRIND_MAKE_MEM_DEFINED but only affects those bytes that are already addressable.
• VALGRIND_DISCARD: At some point you may want Valgrind to stop reporting errors in terms of the blocks defined by the previous three macros. To do this, the above macros return a small-integer “block handle”. You can pass this block handle to VALGRIND_DISCARD. After doing so, Valgrind will no longer be able to relate addressing errors to the user-defined block associated with the handle. The permissions settings associated with the handle remain in place; this just affects how errors are reported, not whether they are reported. Returns 1 for an invalid handle and 0 for a valid handle (although passing invalid handles is harmless). Always returns 0 when not run on Valgrind.
• VALGRIND_CHECK_MEM_IS_ADDRESSABLE and VALGRIND_CHECK_MEM_IS_DEFINED: check immediately whether or not the given address range has the relevant property, and if not, print an error message. Also, for the convenience of the client, returns zero if the relevant property holds; otherwise, the returned value is the address of the first byte for which the property is not true. Always returns 0 when not run on Valgrind.
• VALGRIND_CHECK_VALUE_IS_DEFINED: a quick and easy way to find out whether Valgrind thinks a particular value (lvalue, to be precise) is addressable and defined. Prints an error message if not. Returns no value.
• VALGRIND_DO_LEAK_CHECK: runs the memory leak detector right now. Is useful for incrementally checking for leaks between arbitrary places in the program's execution. Returns no value.
• VALGRIND_COUNT_LEAKS: fills in the four arguments with the number of bytes of memory found by the previous leak check to be leaked, dubious, reachable and suppressed. Again, useful in test harness code, after calling VALGRIND_DO_LEAK_CHECK.
• VALGRIND_GET_VBITS and VALGRIND_SET_VBITS: allow you to get and set the V (validity) bits for an address range. You should probably only set V bits that you have got with VALGRIND_GET_VBITS. Only for those who really know what they are doing.