/usr/include/NTL/config_log.h is in libntl-dev 9.9.1-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | // generated by ./configure WIZARD=off SHARED=on NATIVE=off CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2 CXXFLAGS=-g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wall LDFLAGS=-Wl,-z,relro DEF_PREFIX=/usr NTL_GMP_LIP=on SHARED=on NTL_GF2X_LIB=off
// CXXAUTOFLAGS=""
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