# Difficulty using ccall

**URL:** <https://discourse.julialang.org/t/difficulty-using-ccall/90065>\
**Category:** General Usage\
**Tags:** ccall\
**Created:** [November 10, 2022, 6:40pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065 "2022-11-10T18:40:00Z")\
**Posts on this page:** 12\
**Page:** 1

<div class="post-metadata">

**Author:** ![nvenkov1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nvenkov1/32/43679_2.png) [@nvenkov1](https://discourse.julialang.org/u/nvenkov1)\
**Post date:** [November 10, 2022, 6:40pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/1 "2022-11-10T18:40:00Z")

</div>

I have a shared library file called /home/nxf93431/work/test/julia-gram-schmidt/libmean.so which contains a C function double mean(double a, double b) I try to run in Julia with ccall. I do the following:

using Libdl  
push!(Libdl.DL\_LOAD\_PATH, “/home/nxf93431/work/test/julia-gram-schmidt/”)  
ccall((:mean, “libmean”), Float64, (Float64, Float64), 2.0, 5.0)

but I get the following error:

ERROR: could not load library “libmean”  
libmean.so: cannot open shared object file: No such file or directory

So I wonder if I do something wrong, and if so, I would like to know what it is.

---

<div class="post-metadata">

**Author:** ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)\
**Post date:** [November 10, 2022, 7:52pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/2 "2022-11-10T19:52:30Z")

</div>

What I’d do is

```julia
using Libdl
const libmean = dlopen("/home/nxf93431/work/test/julia-gram-schmidt/libmean.so")
@ccall libmean.mean(1.0::Cdouble, 5.0::Cdouble)::Float64

```

Be aware that hardcoding a path on your machine inside the code will make it very non-relocatable (trying to run it on a different machine would obviously fail), but it’s probably ok if this is for your local testing or local deploying.

---

<div class="post-metadata">

**Author:** ![nvenkov1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nvenkov1/32/43679_2.png) [@nvenkov1](https://discourse.julialang.org/u/nvenkov1)\
**Post date:** [November 10, 2022, 9:06pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/3 "2022-11-10T21:06:14Z")

</div>

I tried your approach. It gives me a very long error message with

ERROR: ‘ccall’ requires the compiler

---

<div class="post-metadata">

**Author:** ![gbaraldi](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gbaraldi/32/22101_2.png) [@gbaraldi](https://discourse.julialang.org/u/gbaraldi)\
**Post date:** [November 10, 2022, 9:12pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/4 "2022-11-10T21:12:47Z")

</div>

What was the very long error? Also what kind of system are you using. OS etc. `versioninfo()` would be cool too.

---

<div class="post-metadata">

**Author:** ![nvenkov1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nvenkov1/32/43679_2.png) [@nvenkov1](https://discourse.julialang.org/u/nvenkov1)\
**Post date:** [November 10, 2022, 9:24pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/5 "2022-11-10T21:24:57Z")

</div>

I can unfortunately not copy the message from the terminal I use. But it starts with

Internal error: encountered unexpected error during compilation of top-level scope:  
TypeError(func=:ccall, context=“”, expected=Symbol, got=0x00000000003ce85a0))  
…

At the end, it says

ERROR: ‘ccall’ requires the compiler

My OS is Linux (x86\_64-linux-gnu). I use the version 1.8.1.

---

<div class="post-metadata">

**Author:** ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)\
**Post date:** [November 10, 2022, 10:03pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/6 "2022-11-10T22:03:45Z")

</div>

Educated guess: try to start Julia with

```julia
LD_LIBRARY_PATH="" julia

```

---

<div class="post-metadata">

**Author:** ![nvenkov1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nvenkov1/32/43679_2.png) [@nvenkov1](https://discourse.julialang.org/u/nvenkov1)\
**Post date:** [November 11, 2022, 12:20pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/7 "2022-11-11T12:20:36Z")

</div>

I tried starting Julia as you said. But I still get the same error when using @ccall.

I am a bit disappointed in the Julia documentation ([https://docs.julialang.org/en/v1/manual/calling-c-and-fortran-code/](https://docs.julialang.org/en/v1/manual/calling-c-and-fortran-code/)) on this topic. Not only is there not enough information to run a functional test case, but there is no mention of Libdl and of the macro @ccall as the function ccall is the only method presented there.

---

<div class="post-metadata">

**Author:** ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)\
**Post date:** [November 11, 2022, 12:32pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/8 "2022-11-11T12:32:05Z")

</div>

You will have to provide more information, including the C code, how you compile the library and the _full_ error message, and how you installed julia.

---

<div class="post-metadata">

**Author:** ![nvenkov1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nvenkov1/32/43679_2.png) [@nvenkov1](https://discourse.julialang.org/u/nvenkov1)\
**Post date:** [November 11, 2022, 12:44pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/9 "2022-11-11T12:44:18Z")

</div>

The C code is very basic. Located in /home/nxf93431/work/test/julia-gram-schmidt/calc\_mean.c, I have

```julia
double mean(double a, double b) {
  return (a+b) / 2;
}

```

The makefile I use is

```julia
CC=gcc 
 
CFLAGS=-c -Wall -fPIC
 
SOURCES=calc_mean.c 
OBJECTS=$(SOURCES:.c=.o)
 
.c.o:
	$(CC) $(CFLAGS) $< -o $@
 
lib: $(OBJECTS)
	$(CC) -shared -fPIC -o libmean.so $(OBJECTS)
 
clean:
	rm *.o *.so

```

The complete error message is

```julia
Internal error: encountered unexpected error during compilation of top-level scope:
TypeError(func=:ccall, context="", expected=Symbol, got=0x0000000000ef7eb0)
ijl_type_error_rt at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/rtutils.c:119
ijl_type_error at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/rtutils.c:127
interpret_symbol_arg at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/ccall.cpp:611
emit_ccall at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/ccall.cpp:1280
emit_expr at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:4751
emit_ssaval_assign at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:4315
emit_stmtpos at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:4562 [inlined]
emit_function at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:7416
jl_emit_code at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:7778
jl_emit_codeinst at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:7823
_jl_compile_codeinst at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/jitlayers.cpp:119
jl_generate_fptr_impl at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/jitlayers.cpp:332
jl_compile_method_internal at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2081 [inlined]
jl_compile_method_internal at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2025
_jl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2359 [inlined]
ijl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2374
jl_toplevel_eval_flex at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/toplevel.c:897
jl_toplevel_eval_flex at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/toplevel.c:850
ijl_toplevel_eval_in at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/toplevel.c:965
eval at ./boot.jl:368 [inlined]
eval_user_input at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:151
repl_backend_loop at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:247
start_repl_backend at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:232
#run_repl#47 at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:369
run_repl at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:355
jfptr_run_repl_66557.clone_1 at /home/nxf93431/julia-1.8.1/lib/julia/sys.so (unknown line)
_jl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2367 [inlined]
ijl_apply_generic at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2549
#967 at ./client.jl:419
jfptr_YY.967_49700.clone_1 at /home/nxf93431/julia-1.8.1/lib/julia/sys.so (unknown line)
_jl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2367 [inlined]
ijl_apply_generic at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2549
jl_apply at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/julia.h:1838 [inlined]
jl_f__call_latest at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/builtins.c:774
#invokelatest#2 at ./essentials.jl:729 [inlined]
invokelatest at ./essentials.jl:726 [inlined]
run_main_repl at ./client.jl:404
exec_options at ./client.jl:318
_start at ./client.jl:522
jfptr__start_61720.clone_1 at /home/nxf93431/julia-1.8.1/lib/julia/sys.so (unknown line)
_jl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2367 [inlined]
ijl_apply_generic at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2549
jl_apply at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/julia.h:1838 [inlined]
true_main at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/jlapi.c:575
jl_repl_entrypoint at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/jlapi.c:719
main at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/cli/loader_exe.c:59
__libc_start_main at /lib64/libc.so.6 (unknown line)
unknown function (ip: 0x401098)
__libc_start_main at /lib64/libc.so.6 (unknown line)
unknown function (ip: 0x401098)
Internal error: encountered unexpected error during compilation of top-level scope:
TypeError(func=:ccall, context="", expected=Symbol, got=0x0000000000ef7eb0)
ijl_type_error_rt at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/rtutils.c:119
ijl_type_error at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/rtutils.c:127
interpret_symbol_arg at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/ccall.cpp:611
emit_ccall at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/ccall.cpp:1280
emit_expr at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:4751
emit_ssaval_assign at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:4315
emit_stmtpos at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:4562 [inlined]
emit_function at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:7416
jl_emit_code at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:7778
jl_emit_codeinst at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/codegen.cpp:7823
_jl_compile_codeinst at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/jitlayers.cpp:119
jl_generate_fptr_for_unspecialized_impl at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/jitlayers.cpp:380
jl_compile_method_internal at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2094 [inlined]
jl_compile_method_internal at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2025
_jl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2359 [inlined]
ijl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2374
jl_toplevel_eval_flex at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/toplevel.c:897
jl_toplevel_eval_flex at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/toplevel.c:850
ijl_toplevel_eval_in at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/toplevel.c:965
eval at ./boot.jl:368 [inlined]
eval_user_input at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:151
repl_backend_loop at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:247
start_repl_backend at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:232
#run_repl#47 at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:369
run_repl at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/usr/share/julia/stdlib/v1.8/REPL/src/REPL.jl:355
jfptr_run_repl_66557.clone_1 at /home/nxf93431/julia-1.8.1/lib/julia/sys.so (unknown line)
_jl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2367 [inlined]
ijl_apply_generic at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2549
#967 at ./client.jl:419
jfptr_YY.967_49700.clone_1 at /home/nxf93431/julia-1.8.1/lib/julia/sys.so (unknown line)
_jl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2367 [inlined]
ijl_apply_generic at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2549
jl_apply at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/julia.h:1838 [inlined]
jl_f__call_latest at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/builtins.c:774
#invokelatest#2 at ./essentials.jl:729 [inlined]
invokelatest at ./essentials.jl:726 [inlined]
run_main_repl at ./client.jl:404
exec_options at ./client.jl:318
_start at ./client.jl:522
jfptr__start_61720.clone_1 at /home/nxf93431/julia-1.8.1/lib/julia/sys.so (unknown line)
_jl_invoke at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2367 [inlined]
ijl_apply_generic at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/gf.c:2549
jl_apply at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/julia.h:1838 [inlined]
true_main at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/jlapi.c:575
jl_repl_entrypoint at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/src/jlapi.c:719
main at /cache/build/default-amdci5-0/julialang/julia-release-1-dot-8/cli/loader_exe.c:59
__libc_start_main at /lib64/libc.so.6 (unknown line)
unknown function (ip: 0x401098)
ERROR: `ccall` requires the compiler

```

---

<div class="post-metadata">

**Author:** ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)\
**Post date:** [November 11, 2022, 12:53pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/10 "2022-11-11T12:53:55Z")

</div>

How did you install Julia? The only way I know to get the error you posted is when the julia process picks up an old libstdc++ from the system (and the error should be made much clearer by [`load_library()` panics on errors when `err=0` by apaz-cli · Pull Request #47343 · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/pull/47343)). Can you please show _ **exactly** _ how you’re starting julia?

> [@nvenkov1](#):
>
> I am a bit disappointed in the Julia documentation ([https://docs.julialang.org/en/v1/manual/calling-c-and-fortran-code/](https://docs.julialang.org/en/v1/manual/calling-c-and-fortran-code/)) on this topic. Not only is there not enough information to run a functional test case, but there is no mention of Libdl and of the macro @ccall as the function ccall is the only method presented there.

That has been already changed in the documentation of v1.9 (not yet released): [Calling C and Fortran Code · The Julia Language](https://docs.julialang.org/en/v1.9-dev/manual/calling-c-and-fortran-code/).

---

<div class="post-metadata">

**Author:** ![GunnarFarneback](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gunnarfarneback/32/1827_2.png) [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)\
**Post date:** [November 11, 2022, 1:04pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/11 "2022-11-11T13:04:17Z")

</div>

Your C code and Makefile are fine. This is what I get with those files:

```julia
$ make
gcc -c -Wall -fPIC calc_mean.c -o calc_mean.o
gcc -shared -fPIC -o libmean.so calc_mean.o
$ julia 
               _
   _ _ _(_)_ | Documentation: https://docs.julialang.org
  (_) | (_) (_) |
   _ _ _| |_ __ _ | Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` | |
  | | |_| | | | (_| | | Version 1.8.0 (2022-08-17)
 _/ |\ __'_|_|_|\__'_| | Official https://julialang.org/ release
|__/ |

julia> ccall((:mean, "./libmean.so"), Cdouble, (Cdouble, Cdouble), 1.0, 2.0)
1.5

```

I agree that something seems to be strange with your Julia installation and/or runtime environment.

---

<div class="post-metadata">

**Author:** ![nvenkov1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nvenkov1/32/43679_2.png) [@nvenkov1](https://discourse.julialang.org/u/nvenkov1)\
**Post date:** [November 11, 2022, 1:15pm UTC](https://discourse.julialang.org/t/difficulty-using-ccall/90065/12 "2022-11-11T13:15:30Z")

</div>

This works! I guess the solution is to give the exact path to the library within the ccall method, there is no need to use Libdl.