(gdb) bt

#0  Curl_strncasecompare (first=0x7000700070006 <error: Cannot access memory at address 0x7000700070006>, second=second@entry=0x7f522c12711c "User-Agent", max=max@entry=10)
    at ../../lib/strcase.c:210
#1  0x00007f522c0e122e in Curl_checkheaders (conn=conn@entry=0x7f520c0ebe60, thisheader=thisheader@entry=0x7f522c12711c "User-Agent") at ../../lib/transfer.c:101
#2  0x00007f522c0cbf4f in Curl_http (conn=0x7f520c0ebe60, done=<optimized out>) at ../../lib/http.c:2110
#3  0x00007f522c0ecfde in multi_do (data=0x7f520c006c90, data=0x7f520c006c90, done=0x7f522d271599) at ../../lib/multi.c:1412
#4  multi_runsingle (multi=0x7f520c001650, now=..., data=0x7f520c006c90) at ../../lib/multi.c:1873
#5  0x00007f522c0eddc1 in curl_multi_perform (multi=multi@entry=0x7f520c001650, running_handles=running_handles@entry=0x7f522d271708) at ../../lib/multi.c:2384
#6  0x00007f522c0e3e03 in easy_transfer (multi=<optimized out>) at ../../lib/easy.c:602
#7  easy_perform (events=false, data=0x7f520c006c90) at ../../lib/easy.c:691
#8  curl_easy_perform (data=0x7f520c006c90) at ../../lib/easy.c:710
#9  0x00007f520b9eb219 in acf_curl_helper (chan=chan@entry=0x7f51a403e690, args=args@entry=0x7f522d271990) at func_curl.c:731
#10 0x00007f520b9ebb71 in acf_curl_exec (chan=0x7f51a403e690, cmd=<optimized out>, info=0x7f522d271a15 "https://xxxxxxxx.xxxxxxx.xx/api/agi/save_callrecord", 
    buf=0x7f522d271a80, len=0) at func_curl.c:810
#11 0x0000000000518f40 in ast_func_read (chan=chan@entry=0x7f51a403e690, 
    function=function@entry=0x7f522d271b30 "CURL(https://xxxxxxxx.xxxxxxx.xx/api/agi/save_callrecord,id=52483&reason=hangup)", workspace=workspace@entry=0x7f522d273b30 "", 
    len=len@entry=4096) at pbx_functions.c:629
#12 0x000000000051cfba in pbx_substitute_variables_helper_full (c=c@entry=0x7f51a403e690, headp=<optimized out>, 
    cp1=cp1@entry=0x7f522d274b80 "tmptmp=${CURL(${GLOBAL(apiurl)}/agi/save_callrecord,${ARG1})}", cp2=<optimized out>, cp2@entry=0x7f522d275c40 "tmptmp=", 
    count=<optimized out>, count@entry=8191, used=used@entry=0x0) at pbx_variables.c:743
#13 0x000000000051d2d6 in pbx_substitute_variables_helper (c=c@entry=0x7f51a403e690, 
    cp1=cp1@entry=0x7f522d274b80 "tmptmp=${CURL(${GLOBAL(apiurl)}/agi/save_callrecord,${ARG1})}", cp2=cp2@entry=0x7f522d275c40 "tmptmp=", count=count@entry=8191)
    at pbx_variables.c:839
#14 0x0000000000509b89 in pbx_extension_helper (c=c@entry=0x7f51a403e690, con=con@entry=0x0, context=0x7f51a403f050 "agi-callrecord", exten=exten@entry=0x7f51a403f0a0 "s", 
    priority=priority@entry=5, label=label@entry=0x0, callerid=<optimized out>, action=<optimized out>, found=<optimized out>, combined_find_spawn=<optimized out>)
    at pbx.c:2936
#15 0x000000000050b163 in ast_spawn_extension (combined_find_spawn=1, found=<optimized out>, callerid=0x7f51a4042040 "36709788663", priority=5, exten=0x7f51a403f0a0 "s", 
    context=<optimized out>, c=0x7f51a403e690) at pbx.c:4226
#16 ast_pbx_h_exten_run (chan=chan@entry=0x7f51a403e690, context=0x7f522d277cc4 "\001") at pbx.c:4256
#17 0x000000000050cb2a in __ast_pbx_run (c=c@entry=0x7f51a403e690, args=args@entry=0x0) at pbx.c:4617
#18 0x000000000050cd91 in pbx_thread (data=data@entry=0x7f51a403e690) at pbx.c:4724
#19 0x000000000058217e in dummy_start (data=<optimized out>) at utils.c:1249
#20 0x00007f522d8f1432 in start_thread () from /lib64/libpthread.so.0
#21 0x00007f522d680913 in clone () from /lib64/libc.so.6

up
#1  0x00007f522c0e122e in Curl_checkheaders (conn=conn@entry=0x7f520c0ebe60, thisheader=thisheader@entry=0x7f522c12711c "User-Agent") at ../../lib/transfer.c:101
101	    if(strncasecompare(head->data, thisheader, thislen) &&

(gdb) p conn->data->set.headers
$1 = (struct curl_slist *) 0x7f520c0f6b30

(gdb) p *(conn->data->set.headers)
$2 = {data = 0x7f5134001420 "@\024", next = 0x7f51340008d0}