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turtles
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Joined: 31 Dec 2004
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 Posted: Wed Mar 27, 2024 8:20 pm Post subject: playing with poppler how to link c++? |
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Greeting fellow Gentoo's
I am messing around with poppler and learning some c++, just a experimental project
I have a small bit of c++ that I call get-txt that begins like so:
| Code: |
#include <iostream>
#include <algorithm>
#include <poppler-document.h>
#include <poppler-page.h>
using namespace std;
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Now I can make a object file with:
| Code: | | g++ -I/usr/include/poppler/cpp/ -c get-txt.cpp |
But for the last part I think I need .a files:
libpoppler-cpp.a
libpoppler.a
liblcms2.so
libfontconfig.a
libjpeg.a
libfreetype.a
libexpat.a
libz.a
On my Gentoo system I have some similar .so files under /usr/lib64/ is there a good way to use these files off my system in my project?
Thanks in advance
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grknight
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Joined: 20 Feb 2015
Posts: 1660
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| Posted: Wed Mar 27, 2024 8:27 pm Post subject: |
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Use the -l option. e.g. -lpoppler for libpoppler.so
If a package has a pkgconfig file (.pc), try use pkgconfig with the --libs options when possible. |
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turtles
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Joined: 31 Dec 2004
Posts: 1658
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| Posted: Wed Mar 27, 2024 8:58 pm Post subject: |
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Ok thanks
this runs fine:
| Code: | | g++ -I/usr/include/poppler/cpp/ -c src/get-txt.cpp -o build/get-txt.o |
when i run this
| Code: | | g++ -lpoppler build/get-txt.o -o build/get-txt |
I get
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: build/get-txt.o: in function `main':
get-txt.cpp:(.text+0x23e): undefined reference to `poppler::document::load_from_file(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: get-txt.cpp:(.text+0x287): undefined reference to `poppler::document::pages() const'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: get-txt.cpp:(.text+0x2f1): undefined reference to `poppler::document::create_page(int) const'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: get-txt.cpp:(.text+0x319): undefined reference to `poppler::page::text(poppler::rectangle<double> const&) const'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: get-txt.cpp:(.text+0x32c): undefined reference to `poppler::ustring::to_latin1[abi:cxx11]() const'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: get-txt.cpp:(.text+0x374): undefined reference to `poppler::ustring::~ustring()'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: get-txt.cpp:(.text+0x48c): undefined reference to `poppler::ustring::~ustring()'
collect2: error: ld returned 1 exit status
My entire c++ file is here:
https://pastebin.com/r61ugdC1
Its not much
Its not part of a package or anything I am just mucking around learning c++
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Hu
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Joined: 06 Mar 2007
Posts: 21637
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| Posted: Wed Mar 27, 2024 9:13 pm Post subject: |
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| That looks expected. First g++ searches libpoppler.so for symbols to satisfy undefined references. It has no undefined references, so it doesn't pull anything from libpoppler.so. Then it processes your .o file, which adds new undefined references. You never go back to libpoppler.so, so they remain undefined. To solve this, put -lpoppler in the standard position for LINKFLAGS, at the end of the line, not the standard position of LDFLAGS, the start of the line. |
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turtles
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Joined: 31 Dec 2004
Posts: 1658
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| Posted: Wed Mar 27, 2024 9:23 pm Post subject: |
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| Hu wrote: | | That looks expected. First g++ searches libpoppler.so for symbols to satisfy undefined references. It has no undefined references, so it doesn't pull anything from libpoppler.so. Then it processes your .o file, which adds new undefined references. You never go back to libpoppler.so, so they remain undefined. To solve this, put -lpoppler in the standard position for LINKFLAGS, at the end of the line, not the standard position of LDFLAGS, the start of the line. |
Thanks Hu!
Do you mean like this?
| Code: | | g++ build/get-txt.o -lpoppler -o build/get-txt |
I get the same error also.
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Hu
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| Posted: Wed Mar 27, 2024 10:48 pm Post subject: |
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| That is the correct position, yes. You also need to use the correct library, though. Your original message did not state what symbols you need, so grknight pointed you to the main library. On review of your current error, it seems like you need to link to a different library. Based on a dump of the symbols offered by each of the poppler libraries, I think you need poppler-cpp. The poppler documentation may be worth checking on this point. |
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turtles
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Joined: 31 Dec 2004
Posts: 1658
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| Posted: Thu Mar 28, 2024 12:06 am Post subject: |
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Ahh duh of course my list of .a files needs to be all in there:
| Code: | | g++ -lpoppler -lpoppler-cpp -llcms2 -lfontconfig -ljpeg -lfreetype -lexpatw -lz build/get-txt.o -o build/get-txt |
grknight hu thank you both, my program works!
If I was going to make a CMakeLists.txt would I just put them all on a line like so
| Code: | | add_library(poppler poppler-cpp lcms2 fontconfig jpeg freetype expatw z) |
?
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