Can't make: implicit declaration of function ‘http_write_chunked’ - c

Question

I'm trying to compile demo main file (https post with the chunked-encoding data) from github repo using, I have installed libghc-iproute-dev and libnl3.
gcc -o main -Imbedtls/include -fPIC -DHAVE_CONFIG_H -D_U_="attribute((unused))" main.c -O2 mbedtls/library/libmbedx509.a mbedtls/library/libmbedtls.a mbedtls/library/libmbedcrypto.a
I can't compile porgram, here is what I got:
main.c: In function ‘main’:
main.c:133:8: warning: implicit declaration of function ‘http_open_chunked’; did you mean ‘http_read_chunked’? [-Wimplicit-function-declaration]
if(http_open_chunked(&hi2, url) == 0)
^~~~~~~~~~~~~~~~~
http_read_chunked
main.c:137:12: warning: implicit declaration of function ‘http_write_chunked’; did you mean ‘http_read_chunked’? [-Wimplicit-function-declaration]
if(http_write_chunked(&hi2, data, size) != size)
^~~~~~~~~~~~~~~~~~
http_read_chunked
/tmp/cc7m6wMn.o: In function main': main.c:(.text.startup+0x3b): undefined reference to http_init'
main.c:(.text.startup+0x48): undefined reference to http_init' main.c:(.text.startup+0x59): undefined reference to http_open_chunked'
main.c:(.text.startup+0x9e): undefined reference to http_write_chunked' main.c:(.text.startup+0xd3): undefined reference to http_write_chunked'
main.c:(.text.startup+0x120): undefined reference to http_write_chunked' main.c:(.text.startup+0x139): undefined reference to http_strerror'
main.c:(.text.startup+0x157): undefined reference to http_close' main.c:(.text.startup+0x15f): undefined reference to http_close'
main.c:(.text.startup+0x19c): undefine
d reference to `http_read_chunked'
collect2: error: ld returned 1 exit status
I also tried to include netlink libraries, using:
#include <asm/types.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
And try to compile using the line:
gcc -o main -fPIC -DHAVE_CONFIG_H -D_U_="attribute((unused))" -O2 -I/usr/include/libnl3/netlink/ -Imbedtls/include main.c ApiService.c mbedtls/library/libmbedx509.a mbedtls/library/libmbedtls.a mbedtls/library/libmbedcrypto.a
Then I got:
ApiService.c:17:8: warning: implicit declaration of function ‘http_open_chunked’; did you mean ‘http_read_chunked’? [-Wimplicit-function-declaration]
if(http_open_chunked(&hi2, url) == 0)
^~~~~~~~~~~~~~~~~
http_read_chunked
ApiService.c:21:12: warning: implicit declaration of function ‘http_write_chunked’; did you mean ‘http_read_chunked’? [-Wimplicit-function-declaration]
if(http_write_chunked(&hi2, data, size) != size)
^~~~~~~~~~~~~~~~~~
http_read_chunked
ApiService.c: In function ‘getTask’:
ApiService.c:106:5: warning: format not a string literal and no format arguments [-Wformat-security]
sprintf(data, cJSON_Print(task));
^~~~~~~
https.c: In function ‘mbedtls_net_connect_timeout’:
https.c:496:18: error: ‘errno’ undeclared (first use in this function); did you mean ‘h_errno’?
else if( errno == EINPROGRESS )
^~~~~
h_errno
https.c:496:18: note: each undeclared identifier is reported only once for each function it appears in
https.c:496:27: error: ‘EINPROGRESS’ undeclared (first use in this function)
else if( errno == EINPROGRESS )
^~~~~~~~~~~
https.c:515:33: error: ‘EINTR’ undeclared (first use in this function); did you mean ‘NLE_INTR’?
if(errno == EINTR) continue;
^~~~~
NLE_INTR
Makefile:16: recipe for target 'compile' failed
Link to repo https://github.com/HISONA/https_client.
Please help I trying to compile that whole day, nothing works for me.

Answer 1

The implicit declaration of function error means that the compiler cannot locate the function in your workspace. you should indicate to the caller where the http_open_chunked function reside in your code by including the header (.h) file where it is impleented.