How can I choose the mex c object file (.o) output location?

I'm developing a mex function on Mac OS X 10.11, Building with 'Xcode with Clang'. I need the .o files so I can debug and I had this working once before on a different Mac, but mex's behavior seems different now.

I run the following command:

 mex -v mxisscalar.c -outdir /mex/mxiscalar

And the .o files are written to:

/var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14438061018957_17444/

This folder only exists until MEX completes, and then it is deleted. How do I output the .o files to somewhere reasonable and prevent them from being automatically deleted?

Output of the MEX:

Verbose mode is on.
Neither -compatibleArrayDims nor -largeArrayDims is selected.
   Using -compatibleArrayDims. In the future, MATLAB will require the use of
   -largeArrayDims and remove the -compatibleArrayDims option.
   For more information:
   http://www.mathworks.com/help/matlab/matlab_external/upgrading-mex-files-to-use-64-bit-api.html.
... Looking for compiler 'Xcode with Clang' ...
... Looking for environment variable 'DEVELOPER_DIR' ...No.
... Executing command 'xcode-select -print-path' ...Yes ('/Applications/Xcode.app/Contents/Developer').
... Looking for folder '/Applications/Xcode.app/Contents/Developer' ...Yes.
... Executing command 'which xcrun' ...Yes ('/usr/bin/xcrun').
... Looking for folder '/usr/bin' ...Yes.
... Executing command 'defaults read com.apple.dt.Xcode IDEXcodeVersionForAgreedToGMLicense' ...No.
... Executing command 'defaults read /Library/Preferences/com.apple.dt.Xcode IDEXcodeVersionForAgreedToGMLicense' ...Yes ('8.0').
... Executing command '
agreed=8.0 
if echo $agreed | grep -E '[\.\"]' >/dev/null; then 
lhs=`expr "$agreed" : '\([0-9]*\)[\.].*'` 
rhs=`expr "$agreed" : '[0-9]*[\.]\(.*\)$'` 
if echo $rhs | grep -E '[\."]' >/dev/null; then 
rhs=`expr "$rhs" : '\([0-9]*\)[\.].*'` 
fi 
if [ $lhs -gt 4 ] || ( [ $lhs -eq 4 ] && [ $rhs -ge 3 ] ); then 
echo $agreed 
else 
exit 1
fi 
fi' ...Yes ('8.0').
... Executing command 'xcode-select -print-path' ...Yes ('/Applications/Xcode.app/Contents/Developer').
... Looking for folder '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk' ...Yes.
... Executing command 'xcode-select -print-path' ...Yes ('/Applications/Xcode.app/Contents/Developer').
... Looking for folder '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk' ...Yes.
... Executing command 'echo /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk | rev | cut -c1-10 | rev | egrep -oh '[0-9]+\.[0-9]+'' ...Yes ('10.12').
Found installed compiler 'Xcode with Clang'.
Options file details
-------------------------------------------------------------------
  Compiler location: /Applications/Xcode.app/Contents/Developer
  Options file: /Users/gregoryallan/Library/Application Support/MathWorks/MATLAB/R2016b/mex_C_maci64.xml
  CMDLINE200 : /usr/bin/xcrun -sdk macosx10.12 clang -Wl,-twolevel_namespace -undefined error -arch x86_64 -mmacosx-version-min=10.9 -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -bundle  -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/mexFunction.map" /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/mxisscalar.o /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/c_mexapi_version.o  -O -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/c_exportsmexfileversion.map"  -L"/Applications/MATLAB_R2016b.app/bin/maci64" -lmx -lmex -lmat -lc++ -o /mex/mxiscalar/mxisscalar.mexmaci64
  CC : /usr/bin/xcrun -sdk macosx10.12 clang
  DEFINES : -DMX_COMPAT_32   -DMATLAB_MEX_FILE
  MATLABMEX : -DMATLAB_MEX_FILE
  MACOSX_DEPLOYMENT_TARGET : 10.9
  CFLAGS : -fno-common -arch x86_64 -mmacosx-version-min=10.9 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk
  INCLUDE : -I"/Applications/MATLAB_R2016b.app/extern/include" -I"/Applications/MATLAB_R2016b.app/simulink/include"
  COPTIMFLAGS : -O2 -fwrapv -DNDEBUG
  CDEBUGFLAGS : -g
  LD : /usr/bin/xcrun -sdk macosx10.12 clang
  LDFLAGS : -Wl,-twolevel_namespace -undefined error -arch x86_64 -mmacosx-version-min=10.9 -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -bundle  -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/mexFunction.map"
  LDBUNDLE : -bundle 
  FUNCTIONMAP : "/Applications/MATLAB_R2016b.app/extern/lib/maci64/mexFunction.map"
  VERSIONMAP : "/Applications/MATLAB_R2016b.app/extern/lib/maci64/c_exportsmexfileversion.map"
  LINKEXPORT : -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/mexFunction.map"
  LINKEXPORTVER : -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/c_exportsmexfileversion.map"
  LINKLIBS : -L"/Applications/MATLAB_R2016b.app/bin/maci64" -lmx -lmex -lmat -lc++
  LDOPTIMFLAGS : -O
  LDDEBUGFLAGS : -g
  OBJEXT : .o
  LDEXT : .mexmaci64
  SETENV : CC="/usr/bin/xcrun -sdk macosx10.12 clang"
CXX="/usr/bin/xcrun -sdk macosx10.12 clang"
CFLAGS="-fno-common -arch x86_64 -mmacosx-version-min=10.9 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -DMX_COMPAT_32   -DMATLAB_MEX_FILE"
CXXFLAGS="-fno-common -arch x86_64 -mmacosx-version-min=10.9 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -DMX_COMPAT_32   -DMATLAB_MEX_FILE"
COPTIMFLAGS="-O2 -fwrapv -DNDEBUG"
CXXOPTIMFLAGS="-O2 -fwrapv -DNDEBUG"
CDEBUGFLAGS="-g"
CXXDEBUGFLAGS="-g"
LD="/usr/bin/xcrun -sdk macosx10.12 clang"
LDXX="/usr/bin/xcrun -sdk macosx10.12 clang"
LDFLAGS="-Wl,-twolevel_namespace -undefined error -arch x86_64 -mmacosx-version-min=10.9 -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -bundle  -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/mexFunction.map" -L"/Applications/MATLAB_R2016b.app/bin/maci64" -lmx -lmex -lmat -lc++ -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/mexFunction.map""
LDDEBUGFLAGS="-g"
  DEVELOPER_DIR_CHECK : 
  XCODE_DIR : /Applications/Xcode.app/Contents/Developer
  XCRUN_DIR : /usr/bin
  XCODE_AGREED_VERSION : 8.0
  ISYSROOT : /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk
  SDKVER : 10.12
  MATLABROOT : /Applications/MATLAB_R2016b.app
  ARCH : maci64
  SRC : /mex/mxisscalar/mxisscalar.c;/Applications/MATLAB_R2016b.app/extern/version/c_mexapi_version.c
  OBJ : /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/mxisscalar.o;/var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/c_mexapi_version.o
  OBJS : /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/mxisscalar.o /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/c_mexapi_version.o 
  SRCROOT : /mex/mxisscalar/mxisscalar
  DEF : /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/mxisscalar.def
  EXP : /mex/mxiscalar/mxisscalar.exp
  LIB : /mex/mxiscalar/mxisscalar.lib
  EXE : /mex/mxiscalar/mxisscalar.mexmaci64
  ILK : /mex/mxiscalar/mxisscalar.ilk
  MANIFEST : /mex/mxiscalar/mxisscalar.mexmaci64.manifest
  TEMPNAME : /mex/mxiscalar/mxisscalar
  EXEDIR : /mex/mxiscalar/
  EXENAME : mxisscalar
  OPTIM : -O2 -fwrapv -DNDEBUG
  LINKOPTIM : -O
  CMDLINE100_0 : /usr/bin/xcrun -sdk macosx10.12 clang -c -DMX_COMPAT_32   -DMATLAB_MEX_FILE -I"/Applications/MATLAB_R2016b.app/extern/include" -I"/Applications/MATLAB_R2016b.app/simulink/include" -fno-common -arch x86_64 -mmacosx-version-min=10.9 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -O2 -fwrapv -DNDEBUG /mex/mxisscalar/mxisscalar.c -o /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/mxisscalar.o
  CMDLINE100_1 : /usr/bin/xcrun -sdk macosx10.12 clang -c -DMX_COMPAT_32   -DMATLAB_MEX_FILE -I"/Applications/MATLAB_R2016b.app/extern/include" -I"/Applications/MATLAB_R2016b.app/simulink/include" -fno-common -arch x86_64 -mmacosx-version-min=10.9 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -O2 -fwrapv -DNDEBUG /Applications/MATLAB_R2016b.app/extern/version/c_mexapi_version.c -o /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/c_mexapi_version.o
-------------------------------------------------------------------
Building with 'Xcode with Clang'.
/usr/bin/xcrun -sdk macosx10.12 clang -c -DMX_COMPAT_32   -DMATLAB_MEX_FILE -I"/Applications/MATLAB_R2016b.app/extern/include" -I"/Applications/MATLAB_R2016b.app/simulink/include" -fno-common -arch x86_64 -mmacosx-version-min=10.9 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -O2 -fwrapv -DNDEBUG /mex/mxisscalar/mxisscalar.c -o /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/mxisscalar.o
/usr/bin/xcrun -sdk macosx10.12 clang -c -DMX_COMPAT_32   -DMATLAB_MEX_FILE -I"/Applications/MATLAB_R2016b.app/extern/include" -I"/Applications/MATLAB_R2016b.app/simulink/include" -fno-common -arch x86_64 -mmacosx-version-min=10.9 -fexceptions -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -O2 -fwrapv -DNDEBUG /Applications/MATLAB_R2016b.app/extern/version/c_mexapi_version.c -o /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/c_mexapi_version.o
/usr/bin/xcrun -sdk macosx10.12 clang -Wl,-twolevel_namespace -undefined error -arch x86_64 -mmacosx-version-min=10.9 -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -bundle  -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/mexFunction.map" /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/mxisscalar.o /var/folders/vh/k8t5_9s13bl4cn8rhc8dhngh0000gn/T/mex_14446221666685_17444/c_mexapi_version.o  -O -Wl,-exported_symbols_list,"/Applications/MATLAB_R2016b.app/extern/lib/maci64/c_exportsmexfileversion.map"  -L"/Applications/MATLAB_R2016b.app/bin/maci64" -lmx -lmex -lmat -lc++ -o /mex/mxiscalar/mxisscalar.mexmaci64
MEX completed successfully.

Answer 1

[David Fink]

To debug, you need to add the debug flag -g so that mex knows to compile with debugging symbols:

mex -g -v mxisscalar.c -outdir /mex/mxiscalar

I just tried this with the yprime.c example on Mac OS 10.11.6, and the .mexmaci64 and .o files were both placed in the directory given by -outdir.