I have some undefined reference errors in an Apache module. I've cut the source code down to a minimum that reproduced the error. Below is the source for "mod_test.c" ...
#include "httpd.h"
#include "http_config.h"
#include "http_request.h"
#include "http_protocol.h"
#include "http_core.h"
#include "http_main.h"
#include "http_log.h"
#include "ap_mpm.h"
#include "apr_strings.h"
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netdb.h>
module AP_MODULE_DECLARE_DATA test_module;
static int test_handler(request_rec *r);
static int test_init(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *s);
/* Structure containing state information for the module */
typedef struct {
} ns_mod_config;
static int ns_typematch(request_rec *r) {
ns_mod_config *ns_scfg = ap_get_module_config(r->server->module_config,
&test_module);
core_request_config *creq_cfg;
creq_cfg = ap_get_core_module_config(r->request_config);
return 0;
}
module AP_MODULE_DECLARE_DATA test_module = {
STANDARD20_MODULE_STUFF,NULL,NULL,NULL,NULL,NULL,NULL};
I am using a more-or-less standard Makefile for compiling the module (note that the install option has been removed as this is a test to demonstrate the problem.)
APXS=/usr/local/apache2/bin/apxs
APXS_OPTS=-Wc, -Wc,-DDST_CLASS=3
SRC=src/mod_test.c
OBJ=src/.libs/mod_test.so
$(OBJ): $(SRC)
#echo
$(APXS) $(APXS_OPTS) -c $(SRC)
#echo
#echo write '"make install"' to install module
#echo
clean:
rm -f src/.libs/*
rm -f src/*.o
rm -f src/*.lo
rm -f src/*.la
rm -f src/*.slo
rmdir src/.libs
The compile fails as follows:
/usr/local/apache2/bin/apxs -Wc, -Wc,-DDST_CLASS=3 -c src/mod_test.c
/usr/local/apache2/build/libtool --silent --mode=compile gcc -prefer-pic -DLINUX -D_REENTRANT -D_GNU_SOURCE -D_LARGEFILE64_SOURCE -g -O2 -pthread -I/usr/local/apache2/include -I/usr/local/apache2/include -I/usr/local/apache2/include -DDST_CLASS=3 -c -o src/mod_test.lo src/mod_test.c && touch src/mod_test.slo
src/mod_test.c: In function âns_typematchâ:
src/mod_test.c:34:3: error: unknown type name âcore_request_configâ
core_request_config *creq_cfg;
^~~~~~~~~~~~~~~~~~~
src/mod_test.c:35:14: warning: implicit declaration of function âap_get_core_module_configâ [-Wimplicit-function-declaration]
creq_cfg = ap_get_core_module_config(r->request_config);
^~~~~~~~~~~~~~~~~~~~~~~~~
src/mod_test.c:35:12: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
creq_cfg = ap_get_core_module_config(r->request_config);
^
apxs:Error: Command failed with rc=65536
.
Makefile:23: recipe for target 'src/.libs/mod_test.so' failed
make: *** [src/.libs/mod_test.so] Error 1
I am not sure how this can occur. http_core.h is present in /usr/local/apache2/include and it does include the definitions that are claimed missing by the compile. Six other modules on the same system compile without errors, though none of them use this specific reference to the core data structures.
Help will be gratefully received.
After posting to the Apache modules mailing list, it develops that the problem is in two parts.
Defining CORE_PRIVATE is required under Apache 2.2 to have access to the core data structures.
ap_get_core_module_config is an Apache 2.4 construct.
Related
I'm trying to call some objective-c code from within ocaml.
stubs.m
#include <Cocoa/Cocoa.h>
#define CAML_NAME_SPACE
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/callback.h>
#include <caml/alloc.h>
#include <caml/fail.h>
CAMLprim value ml_NSLog (value str)
{
CAMLparam1 (str);
NSLog (#"%s", String_val (str));
CAMLreturn (Val_unit);
}
It gets compiled with the following command to stubs.o:
cc -Wextra -Wall -Werror -O -g -std=c99 -pedantic-errors -Wsign-compare -Wshadow -I /Users/Iwan/.opam/4.02.3/lib/ocaml -c -o stubs.o stubs.m
My ocaml code in index.ml is:
external _NSLog: string -> unit = "ml_NSLog"
let log s = _NSLog s
let () = log "hello"
When I execute ocamlopt -o app index.ml stubs.o I get:
Undefined symbols for architecture x86_64:
"_NSLog", referenced from:
_ml_NSLog in stubs.o
(maybe you meant: _ml_NSLog)
"___CFConstantStringClassReference", referenced from:
CFString in stubs.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
File "caml_startup", line 1:
Error: Error during linking
Why do I get the error in this case?
The solution was brutally simple:
ocamlopt -cclib "-framework Cocoa" -o app index.ml stubs.o
I had to pas "-framework Cocoa" as option to the c linker...
I am writing a bluez C program to read battery service. I am using CMake for building the code.
My Cmake File is :
# CMakeLists file for module-bluez project
cmake_minimum_required(VERSION 3.02)
project (bluez-module)
find_package(PkgConfig REQUIRED)
# Adding dbus library
pkg_check_modules(DBUS REQUIRED dbus-1>= 1.6)
include_directories(${DBUS_INCLUDE_DIRS})
link_directories(${DBUS_LIBRARY_DIRS})
#Adding glib library
pkg_check_modules(GLIB REQUIRED glib-2.0>=2.23)
include_directories(${GLIB_INCLUDE_DIRS})
link_directories(${GLIB_LIBRARY_DIRS})
pkg_check_modules (DBUSGLIB REQUIRED dbus-glib-1)
include_directories(${DBUSGLIB_INCLUDE_DIRS})
link_directories(${DBUSGLIB_LIBRARY_DIRS})
# Adding bluetooth using extra libs
list(APPEND EXTRA_LIBS "bluetooth")
# Expose 'gattlib.h' to all sub-directories
include_directories(include)
add_executable(bluez-module scantest.c)
# Linking libraries
message(${DBUSGLIB_LIBRARIES})
target_link_libraries(bluez-module ${EXTRA_LIBS})
#target_link_libraries(bluez-module ${DBUS_LIBRARIES})
target_link_libraries(bluez-module ${DBUSGLIB_LIBRARIES})
target_link_libraries(bluez-module ${GLIB_LIBRARIES})
I have to use g_main_loop in my code. But after building the source file I always get the below error :
[ 50%] Linking C executable bluez-module
CMakeFiles/bluez-module.dir/scantest.c.o: In function `read_battery_service':
scantest.c:(.text+0x5b8): undefined reference to `g_dbus_setup_bus'
collect2: error: ld returned 1 exit status
My read_battery function code is as below :
int read_battery_service(struct hci_state *current_hci_state , char *dev_addr)
{
GError *error = NULL;
GDBusClient *client;
GOptionContext *context;
context = g_option_context_new(NULL);
main_loop = g_main_loop_new(NULL, FALSE);
dbus_conn = g_dbus_setup_bus(DBUS_BUS_SYSTEM, NULL, NULL);
return 0;
}
Just trying to initialize for to access dbus apis.
I have included these headers in the code
#include <assert.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/hci.h>
#include <bluetooth/hci_lib.h>
#include <stdio.h>
#include <gdbus.h>
#include <glib/gmain.h>
What would be the issue ? Is glib.h contains the function g_main_loop_new ? Where should I find it ? Or Is CMake not linking glib properly ?
Looks like you are missing the gdbus linker flags. Try using
pkg_check_modules (DBUSGLIB REQUIRED dbus-glib-1) and add
target_link_libraries(module-bluez ${DBUS_LIBRARIES} ${DBUSGLIB_LIBRARIES})
and see if it helps.
Thanks for reviewing the problem. There is an object c file called try.m, and I complie it to an object file try.o with the command:
gcc -c try.m -o try.o -framework Foundation
the try.h is
int print_word( void );
The try.m is:
#include "try.h"
#import <Foundation/Foundation.h>
int print_word( void )
{
NSLog (#"say hello");
return 0;
}
Additionly, there is a main.c file, which contain the main() function, and it looks:
#include <stdio.h>
#include "try.h"
int main()
{
printf( "This is main\n");
}
I compile main.c to main.o by the following command:
gcc -o main.o -c main.c
Then, I link the main.o and try.o to form the executable file main:
gcc -o main main.o try.o
After these steps, the following errors happened:
enter image description here
The errors are:
Undefined symbols for architecture x86_64:
"_NSLog", referenced from:
_print_word in try.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
How could these errors be solved?
You need to link against the Foundation framework. You can do it all in a single command: gcc main.c try.m -framework Foundation.
I try to built modular programming Makefile for compiling a module named hello-1.c.
I researched create make file and built video but i couldn't success.
My code :
#include <linux/module.h>
#include <linux/kernel.h>
int init_module(void)
{
printk(KERN_INFO "Hello world \n");
return 0;
}
void cleanup_module(void)
{
printk(KERN_INFO "Goodbye world \n");
}
if you look up youtube modular programming , it tell you how to compile. To learn more on how to compile modules which are not part of the official kernel see file linux/Documentation/kbuild/modules.txt.
Makefile for compiling a module named your-file-name--1.c:
obj-m += your-file-name-1.o
all:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
I have a program that has successfully compiled in the past, but now I get a bunch of errors.The source code is just:
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
int main()
{
int fd;
fd = creat("datafile.dat", S_IREAD | S_IWRITE);
if (fd == -1)
printf("Error in opening datafile.dat\n");
else
{
printf("datafile.dat opened for read/write access\n");
printf("datafile.dat is currently empty\n");
}
close(fd);
exit (0);
}
Now I get the errors:
cre.C:8:54: error: ‘creat’ was not declared in this scope
cre.C:16:17: error: ‘close’ was not declared in this scope
cre.C:17:16: error: ‘exit’ was not declared in this scope
Sometimes I get an error about gxx_personality_v0 instead, and sometimes I get no error at all! I've tried updating gcc, but the problem remains. What's going wrong?
OS UBUNTU 12.1 on vaio laptop
From your error messages I see that you called your file cre.C. gcc is case-sensitive for file names: try naming it cre.c and compiling it.
$ LANG=C cc -o foo foo.C
foo.C: In function 'int main()':
foo.C:8:54: error: 'creat' was not declared in this scope
foo.C:16:17: error: 'close' was not declared in this scope
foo.C:17:16: error: 'exit' was not declared in this scope
but
$ LANG=C cc -o foo foo.c
foo.c: In function 'main':
foo.c:17:9: warning: incompatible implicit declaration of built-in function 'exit' [enabled by default]
As noted in a comment, a file with .C extension is handled by the C++ compiler, thus you are seeing those errors.
Read the man pages for the creat, close, and exit functions.
On my system, creat() requires:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
close() requires:
#include <unistd.h>
and exit() requires:
#include <stdlib.h>
As for why the code was compiling before, it's hard to tell. Perhaps the compiler was being invoked in a more permissive mode that didn't complain about missing function declarations, or perhaps some of the headers you do include have #include directives for the headers you need.