The error /usr/bin/ld: cannot find -l<library> (e.g., -lpng, -ljpeg, -ltiff, -lwebp) means the linker (ld) cannot find the required static or shared libraries for libpng, libjpeg, libtiff, and libwebp. Even though you installed the dependencies in ~/rpm/x86_64/, the linker is not searching that directory for libraries.

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Solution: Tell the Linker Where to Find the Libraries

1. Set LIBRARY_PATH and LD_LIBRARY_PATH

The linker (ld) and runtime linker use these environment variables to locate libraries.

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# For the current session (temporary)
export LIBRARY_PATH=~/rpm/x86_64/usr/lib:$LIBRARY_PATH
export LD_LIBRARY_PATH=~/rpm/x86_64/usr/lib:$LD_LIBRARY_PATH

# For permanent use, add these lines to your ~/.bashrc or ~/.bash_profile
echo 'export LIBRARY_PATH=~/rpm/x86_64/usr/lib:$LIBRARY_PATH' >> ~/.bashrc
echo 'export LD_LIBRARY_PATH=~/rpm/x86_64/usr/lib:$LD_LIBRARY_PATH' >> ~/.bashrc
source ~/.bashrc

Note:

• LIBRARY_PATH is for compile-time linking.
• LD_LIBRARY_PATH is for runtime linking.

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2. Verify Library Files Exist

Ensure the .so (shared object) files for the missing libraries exist in ~/rpm/x86_64/usr/lib/:

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ls ~/rpm/x86_64/usr/lib/libpng*
ls ~/rpm/x86_64/usr/lib/libjpeg*
ls ~/rpm/x86_64/usr/lib/libtiff*
ls ~/rpm/x86_64/usr/lib/libwebp*

If they are missing, you need to install the development packages for these libraries (e.g., libpng-devel, libjpeg-turbo-devel, libtiff-devel, libwebp-devel) in your ~/rpm/x86_64/ directory.

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3. Reinstall Dependencies in the Correct Location

If the libraries are missing, reinstall them in ~/rpm/x86_64/ using rpm or yum:

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# Example for libpng (adjust for your RPMs)
rpm -ivh --prefix=~/rpm/x86_64 libpng-devel-*.rpm
rpm -ivh --prefix=~/rpm/x86_64 libjpeg-turbo-devel-*.rpm
rpm -ivh --prefix=~/rpm/x86_64 libtiff-devel-*.rpm
rpm -ivh --prefix=~/rpm/x86_64 libwebp-devel-*.rpm

Note: Use --prefix to install RPMs in a custom directory.

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4. Pass Linker Flags Explicitly

If the above doesn’t work, explicitly pass the library paths to the build process:

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# Set these before running `uv pip install iio==29`
export CFLAGS="-I~/rpm/x86_64/usr/include"
export LDFLAGS="-L~/rpm/x86_64/usr/lib -lpng -ljpeg -ltiff -lwebp"

uv pip install iio==29

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5. Check for 32-bit vs 64-bit Mismatch

Ensure all libraries are 64-bit (since you’re using x86_64). If you accidentally installed 32-bit libraries, the linker will fail.

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file ~/rpm/x86_64/usr/lib/libpng.so*

Output should include ELF 64-bit.

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6. Debugging the Linker

To see where the linker is searching for libraries:

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ld -v

or

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gcc -v -o /dev/null -lpng

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Summary of Commands to Try

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# 1. Set library paths
export LIBRARY_PATH=~/rpm/x86_64/usr/lib:$LIBRARY_PATH
export LD_LIBRARY_PATH=~/rpm/x86_64/usr/lib:$LD_LIBRARY_PATH

# 2. Verify libraries exist
ls ~/rpm/x86_64/usr/lib/libpng* ~/rpm/x86_64/usr/lib/libjpeg* ~/rpm/x86_64/usr/lib/libtiff* ~/rpm/x86_64/usr/lib/libwebp*

# 3. Reinstall dependencies if missing
rpm -ivh --prefix=~/rpm/x86_64 libpng-devel-*.rpm libjpeg-turbo-devel-*.rpm libtiff-devel-*.rpm libwebp-devel-*.rpm

# 4. Retry installation
uv pip install iio==29

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If the Issue Persists

• Check if the libraries are named differently (e.g., libpng12.so instead of libpng.so).
• Use ldconfig to update the shared library cache (if you have root access):

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  sudo ldconfig

• If you don’t have root access, stick with LIBRARY_PATH and LD_LIBRARY_PATH.