<p dir="auto">While rebuilding packages with Python 3.9.0 on macOS Homebrew (<a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="718139045" data-permission-text="Title is private" data-url="https://github.com/Homebrew/homebrew-core/issues/62560" data-hovercard-type="pull_request" data-hovercard-url="/Homebrew/homebrew-core/pull/62560/hovercard" href="https://github.com/Homebrew/homebrew-core/pull/62560">Homebrew/homebrew-core#62560</a>), we are seeing a failure to build scipy 1.5.2.</p>
<h4 dir="auto">Reproducing code example:</h4>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="/usr/local/opt/python@3.9/bin/python3 setup.py build --fcompiler=gnu95"><pre class="notranslate"><code class="notranslate">/usr/local/opt/python@3.9/bin/python3 setup.py build --fcompiler=gnu95
</code></pre></div>
<h4 dir="auto">Error message:</h4>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="scipy/sparse/linalg/dsolve/SuperLU/SRC/clacon2.c:175:5: error: implicit declaration of function 'ccopy_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/dmach.c:62:9: error: implicitly declaring library function 'strncmp' with type 'int (const char *, const char *, unsigned long)' [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/ilu_cdrop_row.c:196:3: error: implicit declaration of function 'scopy_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/ilu_zdrop_row.c:196:3: error: implicit declaration of function 'dcopy_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/smach.c:62:9: error: implicitly declaring library function 'strncmp' with type 'int (const char *, const char *, unsigned long)' [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/zlacon2.c:175:5: error: implicit declaration of function 'zcopy_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/slacon2.c:160:16: error: implicit declaration of function 'idamax_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]"><pre class="notranslate"><code class="notranslate">scipy/sparse/linalg/dsolve/SuperLU/SRC/clacon2.c:175:5: error: implicit declaration of function 'ccopy_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/dmach.c:62:9: error: implicitly declaring library function 'strncmp' with type 'int (const char *, const char *, unsigned long)' [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/ilu_cdrop_row.c:196:3: error: implicit declaration of function 'scopy_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/ilu_zdrop_row.c:196:3: error: implicit declaration of function 'dcopy_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/smach.c:62:9: error: implicitly declaring library function 'strncmp' with type 'int (const char *, const char *, unsigned long)' [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/zlacon2.c:175:5: error: implicit declaration of function 'zcopy_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
scipy/sparse/linalg/dsolve/SuperLU/SRC/slacon2.c:160:16: error: implicit declaration of function 'idamax_' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
</code></pre></div>
<p dir="auto">Xcode 12 for OS X was just released, and I can't build scipy with it. The command <code class="notranslate">pip3 install . -v --user</code> fails, ending with</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="  error: Command &quot;clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk -I/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include -I/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers -DUSE_VENDOR_BLAS=1 -Iscipy/sparse/linalg/dsolve/SuperLU/SRC -I/private/var/folders/cp/n8wtqs490tq5psknff1hv9qr0000gn/T/pip-build-env-k4q2ai5g/overlay/lib/python3.8/site-packages/numpy/core/include -c scipy/sparse/linalg/dsolve/SuperLU/SRC/clacon2.c -o build/temp.macosx-10.15-x86_64-3.8/scipy/sparse/linalg/dsolve/SuperLU/SRC/clacon2.o -MMD -MF build/temp.macosx-10.15-x86_64-3.8/scipy/sparse/linalg/dsolve/SuperLU/SRC/clacon2.o.d&quot; failed with exit status 1
  Building wheel for scipy (PEP 517): finished with status 'error'
  ERROR: Failed building wheel for scipy
Failed to build scipy
ERROR: Could not build wheels for scipy which use PEP 517 and cannot be installed directly"><pre class="notranslate"><code class="notranslate">  error: Command "clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk -I/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include -I/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers -DUSE_VENDOR_BLAS=1 -Iscipy/sparse/linalg/dsolve/SuperLU/SRC -I/private/var/folders/cp/n8wtqs490tq5psknff1hv9qr0000gn/T/pip-build-env-k4q2ai5g/overlay/lib/python3.8/site-packages/numpy/core/include -c scipy/sparse/linalg/dsolve/SuperLU/SRC/clacon2.c -o build/temp.macosx-10.15-x86_64-3.8/scipy/sparse/linalg/dsolve/SuperLU/SRC/clacon2.o -MMD -MF build/temp.macosx-10.15-x86_64-3.8/scipy/sparse/linalg/dsolve/SuperLU/SRC/clacon2.o.d" failed with exit status 1
  Building wheel for scipy (PEP 517): finished with status 'error'
  ERROR: Failed building wheel for scipy
Failed to build scipy
ERROR: Could not build wheels for scipy which use PEP 517 and cannot be installed directly
</code></pre></div>
<p dir="auto">This may be the same issue as <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="671564581" data-permission-text="Title is private" data-url="https://github.com/scipy/scipy/issues/12656" data-hovercard-type="issue" data-hovercard-url="/scipy/scipy/issues/12656/hovercard" href="https://github.com/scipy/scipy/issues/12656">#12656</a> — at least the error at the end is the same — but that issue was closed while only providing the suggestion to use a different compiler.</p>
<p dir="auto">I am using Xcode 12, plus homebrew's Python 3.8, pip3, and gfortran. Unfortunately, I am really trying to figure out how to get this to build in Sage (sagemath.org), and using a gcc toolchain instead of clang would be, at the least, very inconvenient.</p>