git_index_entry* can't read path on ubuntu. · Issue #35 · libgit2/libgit2 · GitHub
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git_index_entry* can't read path on ubuntu. #35

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git_index_entry* can't read path on ubuntu.#35
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@chobie
chobie
opened on Dec 26, 2010

im tring to use libgit2 on my ubuntu 10.10.
i found Segmentation fault when try to read git_index_entry->path.

git clone https://github.com/libgit2/libgit2.git
cd libgit2
./waf configure
./waf build-shared
sudo ./waf install-shared

cat > git_index_test.c <<EOF
#include <stdio.h>
#include <git2.h>

int main(int argc, char * args[])
{
    git_index_entry *entry;
    git_index *index;
    git_index_open_bare(&index,".git/index");

    git_index_read(index);
    git_index_entrycount(index);
    int offset = git_index_find(index,"README.md");

    entry = git_index_get(index,offset);

    printf("pointer_address: %d\n", entry->path);
    //Segmentation fault on my machine.
    printf("path: %s\n",entry->path);
    git_index_free(index);

    return 0;
}
EOF

gcc -lgit2 -o git_index_test git_index_test.c

./git_index_test
pointer_address: 9
Segmentation fault

I searched reason. but i couldn't understand.
git_index_entry->path readable in git_index_get(). but git_index_entry->path was wrong address in main.

(but ruggaed work well on my machine.probably i missunderstood something...)

Could you please advice me how to fix this probrem?

$ gcc -v
Using built-in specs.
Target: i686-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.4.4-14ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.4 --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=i686-linux-gnu --host=i686-linux-gnu --target=i686-linux-gnu
Thread model: posix
gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5)

Activity

  1. vmg commented on Dec 27, 2010

    @vmg
    vmg
    on Dec 27, 2010
    Member

    Hey chobie, it seems to me that the offset you are getting from git_index_find is actually GIT_ENOTFOUND, because the specified file cannot be found. That's why the lookup with git_index_get is failing and returning a NULL pointer. Can you tell me exactly what's the offset you are getting?

  2. chobie commented on Dec 28, 2010

    @chobie
    chobie
    on Dec 28, 2010
    MemberAuthor

    Hi tanoku. thanks for your reply.

    git init
echo "Hello" > README.md
echo "WORLD" > INSTALL
git add README.md INSTALL
git commit -m "initial commit"

    i put my code on this directory. and just added show offset value feature.

    printf("offset: %d\n",offset);

    compile program

    gcc -lgit2 -O0 -g -o git_index_test git_index_test.c

    check git index file.

    git ls-files --stage
100644 83cf24cdfb4891a36bee93421930dd220766299a 0       INSTALL
100644 e965047ad7c57865823c7d992b1d046ea66edf78 0       README.md

    there is README.md entry on my repository.
    try to execute my program ./git_index_test

    offset:1
pointer_address: 9
Segmentation fault

    i also try gdb ./git_index_test.

    git_index_entry->path is correct in git_index_get().
    but git_index_entry->path was wrong address in main scope.
    (git_index_entry->path was just strdup() string. so i wondered about that.)

    ummmm. I couldn't find this solution because i don't have enough C skill.

    i tried my code in some environment.

    OS: Result
    OS X(snow leopard): OK
    Ubuntu 10.10(gcc-4.4, i686-linux-gnu): Segmentation Fault
    CentOS5.5(with remi repository, gcc-4.1.2 i386-redhat-linux): Segmentation Fault

    rugged work fine on my ubuntu desktop.
    probably i missunderstod something in my code...

  3. chobie commented on Dec 29, 2010

    @chobie
    chobie
    on Dec 29, 2010
    MemberAuthor

    I'm sorry to post so many questions.

    finally, i added -D_FILE_OFFSET_BITS=64 option to compile my code. everything works great :)

    Thank you so much for providing great library.
    then i can enjoy New Year's holidays.

  4. vmg commented on Dec 29, 2010

    @vmg
    vmg
    on Dec 29, 2010
    Member

    Hmmm... I'm opening this bug again. You shouldn't have to force _FILE_OFFSET_BITS to compile the library. I'll look into this, thanks a lot for the warning.

  5. chobie commented on Dec 30, 2010

    @chobie
    chobie
    on Dec 30, 2010
    MemberAuthor

    oh, i have not to force _FILE_OFFSET_BITS to compile my code right?

    just write down my code what reappear this probrem.

    on 32bit machine

    git clone https://github.com/libgit2/libgit2.git
cd libgit2
./waf configure && ./waf build-shared
sudo ./waf install-shared

mkdir ../chobie_test && cd ../chobie_test

git init
echo "Hello" > README.md
echo "WORLD" > INSTALL
git add README.md INSTALL
git commit -m "initial commit"


cat > git_index_test.c <<EOF
#include <stdio.h>
#include <git2.h>

int main(int argc, char * args[])
{
    git_index_entry *entry;
    git_index *index;
    git_index_open_bare(&index,".git/index");

    git_index_read(index);
    git_index_entrycount(index);
    int offset = git_index_find(index,"README.md");
    if(offset == GIT_ENOTFOUND){
      fprintf(stderr,"README.md offset not found\n");
      return 0;
    }

    entry = git_index_get(index,offset);

    printf("pointer_address: %d\n", entry->path);
    printf("path: %s\n",entry->path);
    git_index_free(index);

    return 0;
}
EOF

# something wrong on 32bit machine
gcc -o git_index_test -lgit2 git_index_test.c
./git_index_test
#pointer_address: 9
#Segmentation fault

# works good on 32bit machine
gcc -o git_index_test -lgit2 -D_FILE_OFFSET_BITS=64 git_index_test.c
./git_index_test
#pointer_address: 141451832
#path: README.md

    i found D_FILE_OFFSET_BITS option where rugged generated Makefile on my machine.
    (because rugged work fine on my machine.)

  6. scorpion007-zz commented on Jan 9, 2011

    @scorpion007-zz
    scorpion007-zz
    on Jan 9, 2011

    The problem is that index.c compiles by including the internal src/common.h which defines the correct off_t. But user programs don't have access to that header, so they assume off_t is 32 bits.

    This affects windows versions too.

    User applications need access to the headers defining the right sizes to be compatible (the currently private mingw-compat and msvc-compat.h files)

  7. vmg commented on Jan 10, 2011

    @vmg
    vmg
    on Jan 10, 2011
    Member

    Actually, I've changed the public header to use more generic types (unsigned int instead of off_t), since the file_size entry in the Index is always 32-bits (defined as such in the standard). I think this should fix the problem everywhere.

  8. scorpion007-zz commented on Jan 10, 2011

    @scorpion007-zz
    scorpion007-zz
    on Jan 10, 2011

    By standard, you mean the git ABI?

  9. pks-t
    added a commit that references this issue on Jun 7, 2017

    sha1dc: update to fix errors with endianess and unaligned access

    63d86c2
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