• Jeremy (14/14) Mar 12 2023 Hello, I am new to this forum and to D.
• Mike Parker (25/39) Mar 13 2023 That's a linker error, meaning the missing symbol isn't available
• Jeremy (2/28) Mar 13 2023 Okay, thanks.

Jeremy <jtbx disroot.org> writes:

Hello, I am new to this forum and to D.

I am trying to compile a basic D program with libraries 
(`requests` which requires `cachetools` and `automem`) without 
using dub. I have never used dub before, only a compiler.

The folders containing the libraries are in the same folder as 
main.d, the file I am trying to compile, and the command I am 
using to compile is `ldc2 -I. main.d`.

When I compile my program, I just get linker errors such as:
```
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld:
main.o: in function `_Dmain':
main.d:(.text._Dmain+0x2f): undefined reference to 
`_D8requests10getContentFNcAyaZSQBd7streams__T6BufferThZQk'
```

Does anyone have any advice on how to solve my problem?

Mike Parker <aldacron gmail.com> writes:

On Monday, 13 March 2023 at 05:05:27 UTC, Jeremy wrote:
 Hello, I am new to this forum and to D.

 I am trying to compile a basic D program with libraries 
 (`requests` which requires `cachetools` and `automem`) without 
 using dub. I have never used dub before, only a compiler.

 The folders containing the libraries are in the same folder as 
 main.d, the file I am trying to compile, and the command I am 
 using to compile is `ldc2 -I. main.d`.

 When I compile my program, I just get linker errors such as:
 ```
 /usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld:
main.o: in function `_Dmain':
 main.d:(.text._Dmain+0x2f): undefined reference to 
 `_D8requests10getContentFNcAyaZSQBd7streams__T6BufferThZQk'
 ```

 Does anyone have any advice on how to solve my problem?

That's a linker error, meaning the missing symbol isn't available 
to link into the executable. You need to compile the source of 
all the libraries you use and make sure the resultant binaries 
are available for the linker to link into the executable.

The -I switch you've passed tells the compiler where to find 
imported modules. The compiler needs parse them to know which 
symbols are available for you to use when it's compiling your 
code. (The current working directory is the default anyway, so 
you don't need to pass `-I.` for that.)

By default, the compiler does not compile imported modules. If 
you add `-i` to the command line, then it will compile all of the 
modules you import (as long as they're in the `-I` path), 
excluding the DRuntime and Phobos modules. It will then also pass 
all of the compiled object files to the linker, so then your 
linker error should go away.

However, when you choose not to use dub, you need to also ensure 
that you are accounting for any special compiler flags the 
libraries you use may require (for example, specific `-version` 
values). If they're configured to compile as static or shared 
libraries, it may be easier just to store the source for each of 
them outside of your project's source tree, use dub to build each 
of them, and then pass the compiled libraries to the compiler 
when you build your program. In that case, you wouldn't use `-i`. 
Just make sure that `-I` is correctly configured in that case.

Jeremy <jtbx disroot.org> writes:

 That's a linker error, meaning the missing symbol isn't 
 available to link into the executable. You need to compile the 
 source of all the libraries you use and make sure the resultant 
 binaries are available for the linker to link into the 
 executable.

 The -I switch you've passed tells the compiler where to find 
 imported modules. The compiler needs parse them to know which 
 symbols are available for you to use when it's compiling your 
 code. (The current working directory is the default anyway, so 
 you don't need to pass `-I.` for that.)

 By default, the compiler does not compile imported modules. If 
 you add `-i` to the command line, then it will compile all of 
 the modules you import (as long as they're in the `-I` path), 
 excluding the DRuntime and Phobos modules. It will then also 
 pass all of the compiled object files to the linker, so then 
 your linker error should go away.

Using `-i` solved my problem, thank you very much!

 However, when you choose not to use dub, you need to also 
 ensure that you are accounting for any special compiler flags 
 the libraries you use may require (for example, specific 
 `-version` values). If they're configured to compile as static 
 or shared libraries, it may be easier just to store the source 
 for each of them outside of your project's source tree, use dub 
 to build each of them, and then pass the compiled libraries to 
 the compiler when you build your program. In that case, you 
 wouldn't use `-i`. Just make sure that `-I` is correctly 
 configured in that case.

Okay, thanks.