如何在Qt Creator中编译运行pjsua2 Demo并解决链接错误

Let’s work through this linking issue together—since the official pjsua2_demo runs perfectly after compiling PJProject, the problem almost certainly lies in how your Qt project is configuring library includes and links. Here are the most effective fixes to try:

1. Verify Your pkg-config Setup in the .pro File #

First, double-check that your Qt project is pulling in all required PJProject components via pkg-config. It’s easy to only link against pjsua2 and miss its dependencies like pjmedia or pjlib-util.

Make sure your .pro file has these lines:

CONFIG += link_pkgconfig
PKGCONFIG += pjsua2

If you compiled PJProject to a custom directory (not system-wide), you’ll need to tell pkg-config where to find the .pc files first. Open a terminal, set the path, then restart Qt Creator:

export PKG_CONFIG_PATH=/path/to/your/pjproject/lib/pkgconfig:$PKG_CONFIG_PATH

2. Manually Add Missing System Dependencies #

The undefined references you’re seeing (gsm_decode, speex_bits_read_from, snd_device_name_hint) come from system libraries that PJProject relies on but aren’t being auto-linked by pkg-config in some cases. Add these directly to your .pro file:

LIBS += -lgsm -lspeex -lasound

This covers the GSM codec, Speex codec, and ALSA audio backend—exactly the components throwing errors.

3. Cross-Check PJProject’s Compile Configuration #

Since the official demo works, you probably have these components enabled, but it’s worth confirming. Navigate to your PJProject build directory and open config_site.h. Look for these defines to ensure they’re set to 1:

#define PJMEDIA_HAS_GSM_CODEC 1
#define PJMEDIA_HAS_SPEEX_CODEC 1
#define PJMEDIA_AUDIO_DEV_HAS_ALSA 1

If any are set to 0, you’ll need to recompile PJProject with these features enabled (using ./configure --enable-gsm --enable-speex --enable-alsa or similar flags).

4. Copy Exact Link Flags from the Official Demo #

If the above steps don’t work, let’s steal the working link command from the official demo. In your PJProject directory, go to pjsip-apps/build/samples, then run:

make V=1 pjsua2_demo

This will print the full compilation and linking command. Look for the part starting with g++ ... -o pjsua2_demo—copy all the -l flags (like -lpjsua2, -lpjmedia-codec2, etc.) and paste them into your Qt .pro file’s LIBS section. This ensures you’re linking every single library the official demo uses.

Final Notes #

Start with step 2 first—it’s the quickest fix for these specific undefined reference errors. If that doesn’t resolve the issue, move to verifying pkg-config paths or copying the official link flags.

内容的提问来源于stack exchange，提问作者Svaba1012