dynamic library issue: dlsym() failing to find smbol
I've been following Apple's Dynamic Library Programming Topics
docs to create and use a runtime-loaded library using dlopen() / dlsym().
It seems I'm getting a failure to find the desired symbol on my Mid 2012 MacBook Air, running macOS Mojave.
Library Source Code
// adder.h
int add(int x);
and
// adder.cpp
#include "adder.h"
int add(int x) {
return (x + 1);
}
Compiled with clang -dynamiclib adder.cpp -o libAdd.A.dylib
Main Source
// main.cpp
#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include "adder.h"
int main() {
void* adder_handle = dlopen("libAdd.A.dylib", RTLD_LOCAL|RTLD_LAZY);
if (!adder_handle) {
printf("[%s] Unable to load library: %snn", __FILE__, dlerror());
exit(EXIT_FAILURE);
}
while(true) {
void* voidptr = dlsym(adder_handle, "add");
int (*add)(int) = (int (*)(int))voidptr;
if (!add) {
printf("[%s] Unable to get symbol: %snn", __FILE__, dlerror());
exit(EXIT_FAILURE);
}
printf("%dn", add(0));
}
dlclose(adder_handle);
return 0;
}
Compiled with clang main.cpp -o main
I've also set the DYLD_LIBRARY_PATH environment variable to ensure the library can be found. Everything compiles ok.
Nevertheless, when I run the main executable, I get the error:
[main.cpp] Unable to get symbol: dlsym(0x7fb180500000, add): symbol not found
Running nm -gC libAdd.A.dylib outputs:
0000000000000fa0 T add(int)
U dyld_stub_binder
Any ideas on what could be wrong, or what I need to do to debug this issue?
Thanks!
c++ dynamic-library
asked Nov 13 '18 at 20:01
Ian TaylorIan Taylor
205212
add a comment |
I've been following Apple's Dynamic Library Programming Topics
docs to create and use a runtime-loaded library using dlopen() / dlsym().
It seems I'm getting a failure to find the desired symbol on my Mid 2012 MacBook Air, running macOS Mojave.
Library Source Code
// adder.h
int add(int x);
and
// adder.cpp
#include "adder.h"
int add(int x) {
return (x + 1);
}
Compiled with clang -dynamiclib adder.cpp -o libAdd.A.dylib
Main Source
// main.cpp
#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include "adder.h"
int main() {
void* adder_handle = dlopen("libAdd.A.dylib", RTLD_LOCAL|RTLD_LAZY);
if (!adder_handle) {
printf("[%s] Unable to load library: %snn", __FILE__, dlerror());
exit(EXIT_FAILURE);
}
while(true) {
void* voidptr = dlsym(adder_handle, "add");
int (*add)(int) = (int (*)(int))voidptr;
if (!add) {
printf("[%s] Unable to get symbol: %snn", __FILE__, dlerror());
exit(EXIT_FAILURE);
}
printf("%dn", add(0));
}
dlclose(adder_handle);
return 0;
}
Compiled with clang main.cpp -o main
I've also set the DYLD_LIBRARY_PATH environment variable to ensure the library can be found. Everything compiles ok.
Nevertheless, when I run the main executable, I get the error:
[main.cpp] Unable to get symbol: dlsym(0x7fb180500000, add): symbol not found
Running nm -gC libAdd.A.dylib outputs:
0000000000000fa0 T add(int)
U dyld_stub_binder
Any ideas on what could be wrong, or what I need to do to debug this issue?
Thanks!
c++ dynamic-library
asked Nov 13 '18 at 20:01
Ian TaylorIan Taylor
205212
Avoid C++ when using shared libraries; if you cannot, at least useextern "C"
– Lorinczy Zsigmond
Nov 13 '18 at 20:38
add a comment |
I've been following Apple's Dynamic Library Programming Topics
docs to create and use a runtime-loaded library using dlopen() / dlsym().
It seems I'm getting a failure to find the desired symbol on my Mid 2012 MacBook Air, running macOS Mojave.
Library Source Code
// adder.h
int add(int x);
and
// adder.cpp
#include "adder.h"
int add(int x) {
return (x + 1);
}
Compiled with clang -dynamiclib adder.cpp -o libAdd.A.dylib
Main Source
// main.cpp
#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include "adder.h"
int main() {
void* adder_handle = dlopen("libAdd.A.dylib", RTLD_LOCAL|RTLD_LAZY);
if (!adder_handle) {
printf("[%s] Unable to load library: %snn", __FILE__, dlerror());
exit(EXIT_FAILURE);
}
while(true) {
void* voidptr = dlsym(adder_handle, "add");
int (*add)(int) = (int (*)(int))voidptr;
if (!add) {
printf("[%s] Unable to get symbol: %snn", __FILE__, dlerror());
exit(EXIT_FAILURE);
}
printf("%dn", add(0));
}
dlclose(adder_handle);
return 0;
}
Compiled with clang main.cpp -o main
I've also set the DYLD_LIBRARY_PATH environment variable to ensure the library can be found. Everything compiles ok.
Nevertheless, when I run the main executable, I get the error:
[main.cpp] Unable to get symbol: dlsym(0x7fb180500000, add): symbol not found
Running nm -gC libAdd.A.dylib outputs:
0000000000000fa0 T add(int)
U dyld_stub_binder
Any ideas on what could be wrong, or what I need to do to debug this issue?
Thanks!
c++ dynamic-library
asked Nov 13 '18 at 20:01
Ian TaylorIan Taylor
205212
I've been following Apple's Dynamic Library Programming Topics
docs to create and use a runtime-loaded library using dlopen() / dlsym().
It seems I'm getting a failure to find the desired symbol on my Mid 2012 MacBook Air, running macOS Mojave.
Library Source Code
// adder.h
int add(int x);
and
// adder.cpp
#include "adder.h"
int add(int x) {
return (x + 1);
}
Compiled with clang -dynamiclib adder.cpp -o libAdd.A.dylib
Main Source
// main.cpp
#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include "adder.h"
int main() {
void* adder_handle = dlopen("libAdd.A.dylib", RTLD_LOCAL|RTLD_LAZY);
if (!adder_handle) {
printf("[%s] Unable to load library: %snn", __FILE__, dlerror());
exit(EXIT_FAILURE);
}
while(true) {
void* voidptr = dlsym(adder_handle, "add");
int (*add)(int) = (int (*)(int))voidptr;
if (!add) {
printf("[%s] Unable to get symbol: %snn", __FILE__, dlerror());
exit(EXIT_FAILURE);
}
printf("%dn", add(0));
}
dlclose(adder_handle);
return 0;
}
Compiled with clang main.cpp -o main
I've also set the DYLD_LIBRARY_PATH environment variable to ensure the library can be found. Everything compiles ok.
Nevertheless, when I run the main executable, I get the error:
[main.cpp] Unable to get symbol: dlsym(0x7fb180500000, add): symbol not found
Running nm -gC libAdd.A.dylib outputs:
0000000000000fa0 T add(int)
U dyld_stub_binder
Any ideas on what could be wrong, or what I need to do to debug this issue?
Thanks!
c++ dynamic-library
c++ dynamic-library
asked Nov 13 '18 at 20:01
Ian TaylorIan Taylor
205212
asked Nov 13 '18 at 20:01
Ian TaylorIan Taylor
205212
asked Nov 13 '18 at 20:01
Ian TaylorIan Taylor
205212
asked Nov 13 '18 at 20:01
Ian TaylorIan Taylor
205212
asked Nov 13 '18 at 20:01
Ian TaylorIan Taylor
205212
205212
Avoid C++ when using shared libraries; if you cannot, at least useextern "C"
– Lorinczy Zsigmond
Nov 13 '18 at 20:38
add a comment |
Avoid C++ when using shared libraries; if you cannot, at least useextern "C"
– Lorinczy Zsigmond
Nov 13 '18 at 20:38
Avoid C++ when using shared libraries; if you cannot, at least use
extern "C"– Lorinczy Zsigmond
Nov 13 '18 at 20:38
Avoid C++ when using shared libraries; if you cannot, at least use
extern "C"– Lorinczy Zsigmond
Nov 13 '18 at 20:38
add a comment |
1 Answer
1
active
oldest
votes
C++ actually mangles the functionname which results in a different symbolname.
Your are able to spot these mangled symbol names using nm -g <yourlib.dylib>
You can change this behavior by wrapping your method into
extern "C" {
int add(int x);
}
answered Nov 13 '18 at 20:10
wiomocwiomoc
441311
@BradAllred can you elaborate a bit on this? the above solution worked just fine with no changes to the main.cpp file, but I was curious whynm -gshowed the symbol name to be_add.
– Ian Taylor
Nov 13 '18 at 20:32
1
> but I was curious whynm -gshowed the symbol name to be_addthis is I think some MacOS specific mangling, linux in fact does this not. It names this symbol justadd
– wiomoc
Nov 13 '18 at 20:38
2
In C++ you could overload functions/methods or have the same functionname in different classes, because of that compiler has to map the function name to unique symbols, he does that using mangling.
– wiomoc
Nov 13 '18 at 20:49
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
C++ actually mangles the functionname which results in a different symbolname.
Your are able to spot these mangled symbol names using nm -g <yourlib.dylib>
You can change this behavior by wrapping your method into
extern "C" {
int add(int x);
}
answered Nov 13 '18 at 20:10
wiomocwiomoc
441311
@BradAllred can you elaborate a bit on this? the above solution worked just fine with no changes to the main.cpp file, but I was curious whynm -gshowed the symbol name to be_add.
– Ian Taylor
Nov 13 '18 at 20:32
1
> but I was curious whynm -gshowed the symbol name to be_addthis is I think some MacOS specific mangling, linux in fact does this not. It names this symbol justadd
– wiomoc
Nov 13 '18 at 20:38
2
In C++ you could overload functions/methods or have the same functionname in different classes, because of that compiler has to map the function name to unique symbols, he does that using mangling.
– wiomoc
Nov 13 '18 at 20:49
add a comment |
C++ actually mangles the functionname which results in a different symbolname.
Your are able to spot these mangled symbol names using nm -g <yourlib.dylib>
You can change this behavior by wrapping your method into
extern "C" {
int add(int x);
}
answered Nov 13 '18 at 20:10
wiomocwiomoc
441311
@BradAllred can you elaborate a bit on this? the above solution worked just fine with no changes to the main.cpp file, but I was curious whynm -gshowed the symbol name to be_add.
– Ian Taylor
Nov 13 '18 at 20:32
1
> but I was curious whynm -gshowed the symbol name to be_addthis is I think some MacOS specific mangling, linux in fact does this not. It names this symbol justadd
– wiomoc
Nov 13 '18 at 20:38
2
In C++ you could overload functions/methods or have the same functionname in different classes, because of that compiler has to map the function name to unique symbols, he does that using mangling.
– wiomoc
Nov 13 '18 at 20:49
add a comment |
C++ actually mangles the functionname which results in a different symbolname.
Your are able to spot these mangled symbol names using nm -g <yourlib.dylib>
You can change this behavior by wrapping your method into
extern "C" {
int add(int x);
}
answered Nov 13 '18 at 20:10
wiomocwiomoc
441311
C++ actually mangles the functionname which results in a different symbolname.
Your are able to spot these mangled symbol names using nm -g <yourlib.dylib>
You can change this behavior by wrapping your method into
extern "C" {
int add(int x);
}
answered Nov 13 '18 at 20:10
wiomocwiomoc
441311
answered Nov 13 '18 at 20:10
wiomocwiomoc
441311
answered Nov 13 '18 at 20:10
wiomocwiomoc
441311
answered Nov 13 '18 at 20:10
wiomocwiomoc
441311
441311
@BradAllred can you elaborate a bit on this? the above solution worked just fine with no changes to the main.cpp file, but I was curious whynm -gshowed the symbol name to be_add.
– Ian Taylor
Nov 13 '18 at 20:32
1
> but I was curious whynm -gshowed the symbol name to be_addthis is I think some MacOS specific mangling, linux in fact does this not. It names this symbol justadd
– wiomoc
Nov 13 '18 at 20:38
2
In C++ you could overload functions/methods or have the same functionname in different classes, because of that compiler has to map the function name to unique symbols, he does that using mangling.
– wiomoc
Nov 13 '18 at 20:49
add a comment |
@BradAllred can you elaborate a bit on this? the above solution worked just fine with no changes to the main.cpp file, but I was curious whynm -gshowed the symbol name to be_add.
– Ian Taylor
Nov 13 '18 at 20:32
1
> but I was curious whynm -gshowed the symbol name to be_addthis is I think some MacOS specific mangling, linux in fact does this not. It names this symbol justadd
– wiomoc
Nov 13 '18 at 20:38
2
In C++ you could overload functions/methods or have the same functionname in different classes, because of that compiler has to map the function name to unique symbols, he does that using mangling.
– wiomoc
Nov 13 '18 at 20:49
@BradAllred can you elaborate a bit on this? the above solution worked just fine with no changes to the main.cpp file, but I was curious why
nm -g showed the symbol name to be _add.– Ian Taylor
Nov 13 '18 at 20:32
@BradAllred can you elaborate a bit on this? the above solution worked just fine with no changes to the main.cpp file, but I was curious why
nm -g showed the symbol name to be _add.– Ian Taylor
Nov 13 '18 at 20:32
1
1
> but I was curious why
nm -g showed the symbol name to be _add this is I think some MacOS specific mangling, linux in fact does this not. It names this symbol just add– wiomoc
Nov 13 '18 at 20:38
> but I was curious why
nm -g showed the symbol name to be _add this is I think some MacOS specific mangling, linux in fact does this not. It names this symbol just add– wiomoc
Nov 13 '18 at 20:38
2
2
In C++ you could overload functions/methods or have the same functionname in different classes, because of that compiler has to map the function name to unique symbols, he does that using mangling.
– wiomoc
Nov 13 '18 at 20:49
In C++ you could overload functions/methods or have the same functionname in different classes, because of that compiler has to map the function name to unique symbols, he does that using mangling.
– wiomoc
Nov 13 '18 at 20:49
add a comment |
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Avoid C++ when using shared libraries; if you cannot, at least use
extern "C"– Lorinczy Zsigmond
Nov 13 '18 at 20:38