Re: [Boost-users] Can a mapped_file larger than 2GB be random seeked?

It doesn't matter. Same code doesn't work when using boost mapped_file. On 05/05/2015 04:47 AM, james wrote:

In the original code you're seeking to FILESIZE - 1, but in this code you're seeking to FILESIZE - 2

On Tuesday, May 5, 2015, Narcélio Filho mailto:narcelio@gmail.com> wrote:

Hi Michael!

>> I'm compiling under Ubuntu 14.10 (amd64): >> >> $ g++ boost-mmap.cpp -lboost_iostreams >> $ ./a.out >> 0 >> 2147493647 >> Segmentation fault (core dumped) >> >> Everything is 64-bits:

> You are certain that 'everything' is 64-bits? Without diving too deep > into any code, this sounds vaguely, suspiciously like a 32-bit > addressing issue. It could even be something as 'simple' as underlying > file API, or other, code using shorts, ints, instead of longs, for > legacy purposes. Or layers built on said underlying API (i.e. boost > wrappers). > >> $ file a.out >> a.out: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically >> linked (uses shared libs), for GNU/Linux 2.6.32, >> BuildID[sha1]=d39e3dc0c99e666631747e496bf798b92e4d4c71, not stripped

Yes, I'm pretty sure that all my system and boost libs are all 64 bits:

$ dpkg --get-selections | grep boost-iostream libboost-iostreams-dev:amd64 install libboost-iostreams1.55-dev:amd64 install libboost-iostreams1.55.0:amd64 install

$ file /usr/lib/x86_64-linux-gnu/libboost_iostreams.so.1.55.0 /usr/lib/x86_64-linux-gnu/libboost_iostreams.so.1.55.0: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, BuildID[sha1]=a4839c7904aba3cb68a66739aa801e4d5d50c14f, stripped

I'm using just boost API, that calls mmap(). Is this a boost bug?

Using mmap() directly, it works as expected:

#include #include #include #include #include

#include <iostream> #include <fstream> #include <cassert>

using namespace std;

int main(int argc, char *argv[]) { const size_t GIGA = 1024l*1024l*1024l; const size_t FILESIZE = 2l * GIGA + 10000;

ofstream block("file", ios::binary | ios::out); assert(block.good());

block.seekp(FILESIZE); block.write("", 1); block.close();

auto fd = open("file", O_RDWR);

if (fd == -1) { perror("Error opening file for reading"); exit(EXIT_FAILURE); }

char *map = (char*)mmap(0, FILESIZE, PROT_WRITE, MAP_SHARED, fd, 0);

if (map == MAP_FAILED) { close(fd); perror("Error mmapping file"); exit(EXIT_FAILURE); }

char buffer[10] = {0};

cout << 0 << endl; lseek(fd, 0, 0); write(fd, buffer, 1);

cout << FILESIZE - 2 << endl; lseek(fd, FILESIZE - 2, 0); write(fd, buffer, 1);

cout << 1l*GIGA << endl; lseek(fd, 1l*GIGA, 0); write(fd, buffer, 1);

if (munmap(map, FILESIZE) == -1) { perror("Error un-mmapping the file"); }

close(fd);

return 0; }

$ g++ --std=c++11 ex.cpp $ ./a.out 0 2147493646 1073741824

-- []s, Narcélio. _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org javascript:; http://lists.boost.org/mailman/listinfo.cgi/boost-users

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-- []s, Narcélio.