I have finished installing libcurl, but it is still illegal to use the curl_easy_init function.

aha_1980

You don't link to the lib.
Try LIBS += -lcurl in the .Pro file.

Edit: Fixed -l

Lee_Corl

@aha_1980 this is my .pro file

jsulm

@aha_1980 said in I have finished installing libcurl, but it is still illegal to use the curl_easy_init function.:

LIBS += -Lcurl

It's

LIBS += -lcurl

@Lee_Corl Are you on Windows or Linux?
If on Windows then please take a look at documentation: https://doc.qt.io/qt-6/qmake-variable-reference.html#libs
Correct is (example):

win32:LIBS += "C:/mylibs/extra libs/extra.lib"

aha_1980

@jsulm Thanks, that was indeed wrong. Probably because it was too early :)

Lee_Corl

@jsulm Windows

jsulm

@Lee_Corl Then fix the LIBS like I wrote

Lee_Corl

@jsulm What is your intention? However, this is still illegal.

jsulm

@Lee_Corl Please read the link I gave you.
On Windows you link *.lib files like:

win32:LIBS += "C:/mylibs/extra libs/extra.lib"

And please post text, not pictures...

Lee_Corl

@jsulm sorry，My intentions are still lawless, and libcurl's functions are still working.

#-------------------------------------------------
#
# Project created by QtCreator 2024-10-14T17:57:32
#
#-------------------------------------------------

QT       += core gui

LIBS += E:/Desktop/IoT_Parking_Lot/curl-8.10.1/builds/libcurl-vc17-x64-debug-dll-ipv6-sspi-schannel/lib/libcurl_debug.lib
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = IoT_Parking_Lot
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0


SOURCES += main.cpp\
        mainwindow.cpp

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

win32: LIBS += -L$$PWD/../curl-8.10.1/builds/libcurl-vc17-x64-debug-dll-ipv6-sspi-schannel/lib/ -llibcurl_debug
win32:LIBS += "E:/Desktop/IoT_Parking_Lot/curl-8.10.1/builds/libcurl-vc17-x64-debug-dll-ipv6-sspi-schannel/lib/libcurl_debug.lib"

INCLUDEPATH += $$PWD/../curl-8.10.1/builds/libcurl-vc17-x64-debug-dll-ipv6-sspi-schannel/include
DEPENDPATH += $$PWD/../curl-8.10.1/builds/libcurl-vc17-x64-debug-dll-ipv6-sspi-schannel/include

This is my path

JonB

@Lee_Corl
If you had posted your original linking error as pasted text rather than screenshot this would all have been easier for us to see.
Your original screenshot shows ld being used as linker and complaining. That means you are using MinGW as your compiler/linker in your kit.
The curl library you are trying to link against is in a vc17 directory and ends in .lib. That means it has been compiled with MSVC.
You cannot mix MinGW and MSVC compiled code.
Either find or compile curl for MinGW, or change compiler of your Qt project to MSVC, or don't bother to use curl.

Lee_Corl

@JonB Finally, I chose Qt under Linux, which is convenient for Windows installation environment. Thank you