That would be because the product nc * ni overflows in
cbuf = buf = CallocCharBuf(nc * ni);
Since we disallow strings with more than 2^31-1 bytes we could test
and reject this. It might be more future-proof to change the
declaration of
int j, ni, nc;
to
R_xlen_t j, ni, nc;
and let the character allocation code reject, but that would create a
memory leak since the Free call isn't reached. This is a problem in
any case though, as
SET_STRING_ELT(s, is, markKnown(cbuf, STRING_ELT(x, ix)));
could throw errors for a number of reasons and then the Free() is not
reached. It would be better to use R_alloc or register a cleanup
function to call Free on a jump.
Best,
luke
On Wed, 1 Jun 2016, Martin Maechler wrote:
We've had this more general topic on R-help, and also in R-devel recently.
There's one case here where I get the feeling R never gets into
swapping but more directly aborts possibly from a bug we can
more easily fix.
Today I've been working (successfully! - not yet committed) at
fixing str() for very large strings.
In this process, I've found that
pc <- function(.) paste(., collapse=".1.2.3.4.5.")
p <- function(.) strrep(pc(.), 64L)
p(p(p(p(LETTERS))))
produces a (memory related) segmentation fault (aka "crash")
very reproducibly and relatively quickly
both on my Linux (Fedora 22) desktop and on our Windows server.
*** caught segfault ***
address 0x7fc52dc89000, cause 'memory not mapped'
Traceback:
1: strrep(pc(.), 64L)
2: p(p(p(p(LETTERS))))
3: system.time(L2 <- p(p(p(p(LETTERS)))))
In the debugger, the symptoms point to the possibility of a
bug just in the C parts of strrep() :
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff54d6223 in __strcpy_sse2_unaligned () from /usr/lib64/libc.so.6
Missing separate debuginfos, use: dnf debuginfo-install
bzip2-libs-1.0.6-14.fc22.x86_64 libgcc-5.3.1-6.fc22.x86_64
libgfortran-5.3.1-6.fc22.x86_64 libgomp-5.3.1-6.fc22.x86_64
libicu-54.1-4.fc22.x86_64 libquadmath-5.3.1-6.fc22.x86_64
libstdc++-5.3.1-6.fc22.x86_64 ncurses-libs-5.9-18.20150214.fc22.x86_64
pcre-8.38-4.fc22.x86_64 readline-6.3-5.fc22.x86_64 xz-libs-5.2.0-2.fc22.x86_64
zlib-1.2.8-7.fc22.x86_64
(gdb) bt
#0 0x00007ffff54d6223 in __strcpy_sse2_unaligned () from /usr/lib64/libc.so.6
#1 0x0000000000457def in do_strrep (call=<optimized out>, op=<optimized out>,
args=<optimized out>,
env=<optimized out>) at ../../../R/src/main/character.c:1658
#2 0x00000000004d6844 in bcEval (body=body@entry=0xd66840,
rho=rho@entry=0x45253b8,
useCache=useCache@entry=TRUE) at ../../../R/src/main/eval.c:5648
#3 0x00000000004dd240 in Rf_eval (e=0xd66840, rho=0x45253b8) at
../../../R/src/main/eval.c:616
#4 0x00000000004dedaf in Rf_applyClosure (call=call@entry=0x45250a8,
op=op@entry=0xd668e8,
arglist=0x45251f8, rho=rho@entry=0x4525000, suppliedvars=0xa57188)
at ../../../R/src/main/eval.c:1134
#5 0x00000000004dd3b1 in Rf_eval (e=0x45250a8, rho=0x4525000) at
../../../R/src/main/eval.c:732
#6 0x00000000004dedaf in Rf_applyClosure (call=call@entry=0x4525718,
op=op@entry=0x4524d28,
arglist=0x4524f90, rho=rho@entry=0xa8ea30, suppliedvars=0xa57188)
at ../../../R/src/main/eval.c:1134
#7 0x00000000004dd3b1 in Rf_eval (e=0x4525718, rho=0xa8ea30) at
../../../R/src/main/eval.c:732
#8 0x00000000004e0cde in do_set (call=0x4525670, op=0xa61358, args=<optimized
out>, rho=0xa8ea30)
at ../../../R/src/main/eval.c:2196
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--
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: [email protected]
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
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