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Diffstat (limited to 'manual/memory.texi')
| -rw-r--r-- | manual/memory.texi | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/manual/memory.texi b/manual/memory.texi index a186fd4b8c..343fcd1c8a 100644 --- a/manual/memory.texi +++ b/manual/memory.texi @@ -975,7 +975,7 @@ main (int argc, char *argv[]) @} @end example -I.e., the user can start the memory debugger any time he wants if the +I.e., the user can start the memory debugger any time s/he wants if the program was started with @code{MALLOC_TRACE} set in the environment. The output will of course not show the allocations which happened before the first signal but if there is a memory leak this will show up @@ -1004,9 +1004,9 @@ readability. Instead there is a program which comes with the GNU C library which interprets the traces and outputs a summary in on user-friendly way. The program is called @code{mtrace} (it is in fact a Perl script) and it takes one or two arguments. In any case the name of -the file with the trace must be specified. If an optional precedes the -name of the trace file this must be the name of the program which -generated the trace. +the file with the trace output must be specified. If an optional argument +precedes the name of the trace file this must be the name of the program +which generated the trace. @example drepper$ mtrace tst-mtrace log @@ -1058,6 +1058,21 @@ Memory not freed: Suddenly the output makes much more sense and the user can see immediately where the function calls causing the trouble can be found. +Interpreting this output is not complicated. There are at most two +different situations being detected. First, @code{free} was called for +pointers which were never returned by one of the allocation functions. +This is usually a very bad problem and how this looks like is shown in +the first three lines of the output. Situations like this are quite +rare and if they appear they show up very drastically: the program +normally crashes. + +The other situation which is much harder to detect are memory leaks. As +you can see in the output the @code{mtrace} function collects all this +information and so can say that the program calls an allocation function +from line 33 in the source file @file{/home/drepper/tst-mtrace.c} four +times without freeing this memory before the program terminates. +Whether this is a real problem keeps to be investigated. + @node Obstacks @section Obstacks @cindex obstacks |