Hi, Otto Moerbeek wrote on Sun, May 19, 2019 at 02:55:09PM +0200: > On Sun, May 19, 2019 at 08:50:20AM +0200, Jan Stary wrote:
>> Does 'J' simply make the junk level two and >> does 'j' simply make the junk level zero? No, it does not. For example, if sysctl vm.malloc_conf contains j and MALLOC_OPTIONS contains J, or if any one source contains "jJ" or "jjJ", you end up with level 1: During the first malloc call in the program, the j first lowers the level from 1 to 0, then the J raises the level back to 1, but not to 2. >> The current "increase/decrease" wording in malloc(3) >> can suggest it has a memory. For example, setting >> >> vm.malloc_conf=J >> >> "increases" junk level to two; >> does setting >> >> vm.malloc_conf=C >> >> later retain a junk level of two, >> as there is no 'j' to "decrease" it, >> or is the junk level the defult of one now? Your question makes no sense whatsoever. First, the word "later" makes no sense. Malloc initialization is only done once during a run of any given program. So if the sysctl contains J during startup, that is what governs program behaviour. Changing the sysctl later no longer has any effect on the running program. Besides, while J and j manipulate mopts.def_malloc_junk, C sets mopts.chunk_canaries. One doesn't have anything to do with the other. > C is a combined flag, containing J amongst others. Neither the code nor the manual page appears to agree with that statement. Are you maybe thinking of S? To provide another example, MALLOC_OPTIONS=jS results in junk level 1 because j lowers it from 1 to 0, then S raises it from 0 to 1. MALLOC_OPTIONS=jSS results in junk level 2, whereas MALLOC_OPTIONS=SSj results in junk level 1. The manual page already seems quite clear. Well, maybe we could add one sentence for even more clarity. Right now, some might think that earlier flags win. OK? Ingo Index: malloc.3 =================================================================== RCS file: /cvs/src/lib/libc/stdlib/malloc.3,v retrieving revision 1.124 diff -u -r1.124 malloc.3 --- malloc.3 13 May 2019 06:04:55 -0000 1.124 +++ malloc.3 19 May 2019 14:39:30 -0000 @@ -270,6 +270,8 @@ in the program. Each is scanned for the flags documented below. Unless otherwise noted uppercase means on, lowercase means off. +During initialization, flags occurring later modify the behaviour +that was requested by flags processed earlier. .Bl -tag -width indent .It Cm C .Dq Canaries .
