Can't compile C program on a Mac after upgrade to Mojave

Question

I have used the gcc command on the terminal to compile C programs but all of a sudden, after an update to my Mac\'s OS (to macOS 10.14 Mojave, and XCode 10.0), I started rec

Answer 1

NOTE: The following is likely highly contextual and time-limited before the switch/general availability of macos Catalina 10.15. New laptop. I am writing this Oct 1st, 2019.

These specific circumstances are, I believe, what caused build problems for me. They may not apply in most other cases.

Context:

• macos 10.14.6 Mojave, Xcode 11.0, right before the launch of macos Catalina 10.15. Newly purchased Macbook Pro.

• failure on pip install psycopg2, which is, basically, a Python package getting compiled from source.

• I have already carried out a number of the suggested adjustments in the answers given here.

My errors:

pip install psycopg2
Collecting psycopg2
  Using cached https://files.pythonhosted.org/packages/5c/1c/6997288da181277a0c29bc39a5f9143ff20b8c99f2a7d059cfb55163e165/psycopg2-2.8.3.tar.gz
Installing collected packages: psycopg2
  Running setup.py install for psycopg2 ... error
    ERROR: Command errored out with exit status 1:
     command: xxxx/venv/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/bk/_1cwm6dj3h1c0ptrhvr2v7dc0000gs/T/pip-install-z0qca56g/psycopg2/setup.py'"'"'; __file__='"'"'/private/var/folders/bk/_1cwm6dj3h1c0ptrhvr2v7dc0000gs/T/pip-install-z0qca56g/psycopg2/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /private/var/folders/bk/_1cwm6dj3h1c0ptrhvr2v7dc0000gs/T/pip-record-ef126d8d/install-record.txt --single-version-externally-managed --compile --install-headers xxx/venv/include/site/python3.6/psycopg2


...
/usr/bin/clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -isysroot/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -DPSYCOPG_VERSION=2.8.3 (dt dec pq3 ext lo64) -DPG_VERSION_NUM=90615 -DHAVE_LO64=1 -I/Users/jluc/kds2/py2/venv/include -I/opt/local/Library/Frameworks/Python.framework/Versions/3.6/include/python3.6m -I. -I/opt/local/include/postgresql96 -I/opt/local/include/postgresql96/server -c psycopg/psycopgmodule.c -o build/temp.macosx-10.14-x86_64-3.6/psycopg/psycopgmodule.o

    clang: warning: no such sysroot directory: 
'/Applications/Xcode.app/Contents/Developer/Platforms
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