Date: Tue, 19 Jun 2012 15:16:50 -0400 From: Rich Felker <dalias@...ifal.cx> To: musl@...ts.openwall.com Cc: bug-gnulib@....org Subject: Re: Re: musl, printf out-of-memory test On Tue, Jun 19, 2012 at 12:45:50PM +0200, Bruno Haible wrote: > So, the exit code 1 must have come from the crash handler. Without this crash > handler: 7x I get > > configure:8919: checking whether printf survives out-of-memory conditions > configure:8979: /arch/x86-linux/inst-musl/bin/musl-gcc -o conftest -g -O2 -Wall conftest.c >&5 > configure:8982: $? = 0 > printf's return value = 5000002, errno = 0 > configure:8986: $? = 0 > configure:9031: result: yes > > but once I get > > configure:8979: /arch/x86-linux/inst-musl/bin/musl-gcc -o conftest -g -O2 -Wall conftest.c >&5 > configure:8982: $? = 0 > configure:8986: $? = 139 > configure:9031: result: no > > So, apparently, under memory stress, musl's printf has a probability of > between 10% and 50% of crashing with SIGSEGV (139 = 128 + 11). musl's printf does not do anything with memory except using a small constant amount of stack space (a few hundred bytes for non-float, somewhere around 5-7k for floating point). This is completely independent of the width/padding/precision; the implementation actually goes to a good bit of trouble to ensure that it can print any amount of padding efficiently without large or unbounded stack space usage. Is there any way the rlimits put in place could be preventing the stack from expanding beyond even one page the current number of pages, etc.? Rich
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