I wrote a C function to be executed from within PostgreSQL (with a CREATE FUNCTION ... LANGUAGE C; command) but when I do so, it responds 'PQnfields: symbol not found'.
I tried to include the path to where the libpq library is when I compile, like this:
gcc -lpq -fpic -c crossdb.c -I`pg_config --includedir-server` -I /usr/include/ -std=c99
But it didn't work.
I think that it is simply not possible to use libpq to query the database from a function... So if you know how to do it or what is causing this error message, I'd be happy to ear it from you.
You'll have to put the directory containing libpq.so.* on PostgreSQL's shared library path, either by setting LD_LIBRARY_PATH in the server's environment or by adding -Wl,-rpath,/path/to/so to the compile line.
Are you using the PGXS framework to build the shared library? That gives you most of the proper flags automatically.
Look at postgres_fdw's Makefile for inspiration, it links with libpq too.
Taking a step back: are you sure that you need a function called crossdb that calls the client? I would investigate if a foreign table or dblink can do what you are trying to achieve.
Related
I wrote a demo using libpq to connect to a PostgreSQL database.
I tried to connect the C file to PostgreSQL by including
#include <libpq-fe.h>
after I added the paths into system variables I:\Program Files\PostgreSQL\12\lib as well as to I:\Program Files\PostgreSQL\12\include and compiled with this command:
gcc -Wall -Wextra -m64 -I "I:\Program Files\PostgreSQL\12\include" -L "I:\Program Files\PostgreSQL\12\lib" testpsql.c -lpq -o testpsql
It first raised three errors, like
libssl-1_1-x64.dll is missing
libintl-8.dll was missing
libcrypto-1_1-x64.dll was missing
After I downloaded these three files and put them into I:\Program Files\PostgreSQL\12\lib, and compiled it again, it shows the error
The application was unable to start correctly (0xc0150002)
when I type testpsql. But if I type ./testpsql on git bash, it works. Anyone can please tell me why?
The code that I used was the first example from here.
Environment: PostgreSQL 12, Windows 10, MinGW64
“Download the DLL files” sounds dangerous. From where?
I would get rid of these files again. Since you probably don't reference these libraries from your code, it must be the dependencies of libpq.dll and are probably found in I:\Program Files\PostgreSQL\12\bin (if you used the EDB installer).
The problem is probably that you the PATH environment variable is different in git bash and in cmd.exe, and in the latter case not all required shared libraries can be found on the PATH. The solution is to change the PATH so that it includes all DLL files the executable requires, not to start copying around files.
It is probably enough to include I:\Program Files\PostgreSQL\12\bin in the PATH. To resolve missing dependencies, use a tool like dependency walker or this replacement.
TL:DR
Can you generate clang debugging information(CFGs, PDGs) when the original source file have DEPENDENCY errors from missing header files that cause compilation issues such as undeclared identifiers and unknown types? The files are syntactically correct. Is there a flag that maybe set all undeclared identifiers to INTs for debugging?
I am using Clang to analyze source code packages. Usually, I modify the makefile so clang generates debugging information using the command below
clang -emit-llvm -g -S -ferror-limit=0 -I somefile some_c_file
However, this approach is very makefile focused and if developer does not support Clang in that given build version, I have to figure out how to generate the debugging information.
This is not good for automation. For things such as OpenSSL where they include dozen of files(headers) and custom configurations for the given platform, this is not practical. I want to suppress or ignore the errors if possible since I know the build version's file under test is syntactically correct.
Thanks!
Recently I used clang-tidy for source code analysis of one of our projects. The project uses GNU compiler and we didn't wanted to move away from that. So the process that I followed was below:
1) Use bear to generate the compilation database i.e. compile_commands.json which is used by clang-tidy
2) By pass the include files that we don't want to analyze by including them as system files i.e. use --isystem for their inclusion and project specific files using -I. (If you can't change the Make files you could change the compile_commands.json by a simple find and replace)
Hope this helps
I apologize if this seems like a stupid question, but I guess I am more used to packages that come with Makefiles or configure scripts.
I downloaded the Mongoose source tar file from the site, and untarred it.
I then tried to compile an executable out of it using
gcc -g -c mongoose.c -o main.o -lpthread -ldl.
However, after trying to execute, I get the error -bash: ./main.o: cannot execute binary file
When I looked into mongoose.c source, I did not find a main function.
Where can I get the main function so that the Linux mongoose web server can be compiled to work the same way as the Windows mongoose.exe?
Mongoose does come with a Makefile, and will compile as a standalone command-line program. Lua and SQLite are included.
The easiest way to compile the latest version is to cd into the "build" directory and run make unix. I'm not sure about the archived version on the downloads page, but trunk has been pretty stable.
I just checked out a clean copy of Mongoose from github earlier tonight and built it with no problems, so I can confirm that this works (assuming you have any other dependencies set up properly, of course).
It's because mongoose is not supposed to be used standalone, but to "embed" it into your program. You need to create a program which calls the correct function from mongoose.c.
Also, the -c flag to GCC tells it to create an object file, which needs to be linked to create an executable. So you try to execute a file which is not executable.
TL;DR - I need to compile archive.a with test.o to make an executable.
Background - I am trying to call a function in a separate library from a software package I am modifying but the function (a string parser) is creating a segmentation violation. The failure is definitely happening in the library and the developer has asked for a test case where the error occurs. Rather than having him try to compile the rather large software package that I'm working on I'd rather just send him a simple program that calls the appropriate function (hopefully dying at the same place). His library makes use of several system libraries as well (lapack, cblas, etc.) so the linking needs to hit everything I think.
I can link to the .o files that are created when I make his library but of course they don't link to the appropriate system libraries.
This seems like it should be straight forward, but it's got me all flummoxed.
The .a extension indicates that it is a static library. So in order to link against it you can use the switches for the linking stage:
gcc -o myprog -L<path to your library> main.o ... -larchive
Generally you use -L to add the path where libraries are stored (unless it is in the current directory) and you use -l<libname> to sepecify a library. The libraryname is without extension. If the library is named libarchive.a you would still give -larchive.
If you want to specify the full name of the library, then you would use i.e. -l:libname.a
update
If the libraypath is /usr/lib/libmylibrary.a you would use
-L/usr/lib -lmylibrary
How do I convince LibTools to generate a library identical to what gcc does automatically?
This works if I do things explicitly:
gcc -o libclique.dylib -shared disc.c phylip.c Slist.c clique.c
cp libclique.dylib [JavaTestDir]/libclique.dylib
But if I do:
Makefile libclique.la (which is what automake generates)
cp .libs/libclique.1.dylib [JavaTestDir]/libclique.dylib
Java finds the library but can't find the entry point.
I read the "How to create a shared library (.so) in an automake script?" thread and it helped a lot. I got the dylib created with a -shared flag (according to the generated Makefile). But when I try to use it from Java Native Access I get a "symbol not found" error.
Looking at the libclique.la that is generated by Makefile it doesn't seem to have any critical information in it, just looks to be link overloads and moving things around for the convenience of subsequent C/C++ compiler steps (which I don't have), so I would expect libclique.1.dylib to be a functioning dynamic library.
I'm guessing that is where I'm going wrong, but, given that JNA links directly to a dylib and is not compiled with it (per the example in the discussion cited above), it seems all the subsequent compilation steps described in the LibTools manual are moot.
Note: I'm testing on a Mac, but I'm going to have to do this on Windows and Linux machines also, which is why I'm trying to put this into Automake.
Note2: I'm using Eclipse for my Java development and, yes, I did import the dylib.
Thanks
You should be building a plugin and in particular pass
libclique_la_LDFLAGS = -avoid-version -module -shared -export-dynamic
This way you tell libtool you want a dynamically loadable module rather than a shared library (which for ELF are the same thing, but for Mach-O are not.)