R 3.6 broke build with gcc 5.3, can't find stdlib.h

Before:

g++ -std=gnu++14 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/RcppEigen/include" -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/StanHeaders/include" -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/BH/include" -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/rpf/include" -I/usr/local/include -fopenmp -Wno-unknown-pragmas -Wno-unused-parameter -Wno-unused-local-typedefs -Wno-deprecated-declarations -Wno-unused-function -Wno-unused-variable -fdiagnostics-color=auto -DEXTRA_GCC_DIAG -Wno-misleading-indentation -Wno-pragmas -Wno-ignored-attributes -mmacosx-version-min=10.7 -I. -Iinclude -Iinclude/zstd-1.1.0 -Iinclude/zstd-1.1.0/common -Iinclude/zstd-1.1.0/compress -Iinclude/zstd-1.1.0/decompress -D SQLITE_ENABLE_COLUMN_METADATA -D SQLITE_ENABLE_STAT4 -D SQLITE_MAX_EXPR_DEPTH=10000 -D SQLITE_USE_URI=1 -fPIC -Wall -g -O2 -c Compute.cpp -o Compute.o

After:

g++ -std=gnu++14 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I"/Library/Frameworks/R.framework/Versions/3.6/Resources/library/Rcpp/include" -I"/Library/Frameworks/R.framework/Versions/3.6/Resources/library/RcppEigen/include" -I"/Library/Frameworks/R.framework/Versions/3.6/Resources/library/StanHeaders/include" -I"/Library/Frameworks/R.framework/Versions/3.6/Resources/library/BH/include" -I"/Library/Frameworks/R.framework/Versions/3.6/Resources/library/rpf/include" -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -I/usr/local/include -fopenmp -Wno-unknown-pragmas -Wno-unused-parameter -Wno-unused-local-typedefs -Wno-deprecated-declarations -Wno-unused-function -Wno-unused-variable -fdiagnostics-color=auto -DEXTRA_GCC_DIAG -Wno-misleading-indentation -Wno-pragmas -Wno-ignored-attributes -mmacosx-version-min=10.7 -I. -Iinclude -Iinclude/zstd-1.1.0 -Iinclude/zstd-1.1.0/common -Iinclude/zstd-1.1.0/compress -Iinclude/zstd-1.1.0/decompress -D SQLITE_ENABLE_COLUMN_METADATA -D SQLITE_ENABLE_STAT4 -D SQLITE_MAX_EXPR_DEPTH=10000 -D SQLITE_USE_URI=1 -fPIC -Wall -g -O2 -c Compute.cpp -o Compute.o

Error:

   In file included from /usr/local/include/c++/5.3.0/bits/stl_algo.h:59:0,
                    from /usr/local/include/c++/5.3.0/algorithm:62,
                    from Compute.cpp:17:
   /usr/local/include/c++/5.3.0/cstdlib:72:20: fatal error: stdlib.h: No such file or directory
   compilation terminated.
   make[1]: *** [Compute.o] Error 1

What’s up with that? stdlib.h should be easy to find. CC @jeroen @jimhester

Why do you use gcc? We usually compile with clang, either from xcode or the cran version with openmp.

Are you running Mojave? Here R 3.6.0 requires you install the SDK headers:

sudo installer -pkg /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg -target /

See also this thread in r-sig-mac: https://stat.ethz.ch/pipermail/r-sig-mac/2019-April/012955.html

Oh, I forgot that CRAN clang started offering OpenMP support since the end of 2018. How can I use CRAN clang on Travis?

No, this is El Capitan (10.11). See example log. Is El Capitan still supported or is it time to upgrade?

It is recommended to upgrade, see also this topic: https://travis-ci.community/t/library-developer-commandlinetools-sdks-macosx-sdk-missing-on-el-capitain