C Configure does not find certain math functions

byrnejb

byrnejb

I am building a 4GL compiler/vm and the configuration script is reporting this:

Code: 
checking for floor... no
checking for pow... no
checking for trunc... no

I am passing this to configure:

Code: 
./configure --prefix=$HOME/usr/local \
>             --exec-prefix=$HOME/usr/local \
>             --with-build-cc=/usr/local/bin/gcc \
>             --with-build-cflags=-lm \
>             --with-build-libs="/lib /usr/lib /usr/local/lib" \
>             --with-iodbc=/usr/local/lib \
>             --with-java=/usr/local/openjdk11 \
>             --with-pgsqleng=/var/db/postgres/data11

I am passing -lm to gcc and libm.so exists:

Code: 
ls -l /usr/lib/libm.so
lrwxr-xr-x  1 root  wheel  19 Nov  1  2019 /usr/lib/libm.so -> ../../lib/libm.so.5


So, what am I missing here?
 
Maybe it's looking for some other math library? Are you sure it's depending on libm.so? Normally you don't need to supply /usr/lib and/or /usr/include because these are searched by default. It's typically /usr/local/lib and /usr/local/include it has problems with.

byrnejb said:
So, what am I missing here?
Click to expand...
Often you can find additional configure options if you run ./configure --help. Perhaps it needs to be set with a specific option.
 
Code: 
  --with-java=path        full path of Java Developers Kit, or no
  --with-build-cc=XXX     the build C compiler ($BUILD_CC)
  --with-build-cflags=XXX the build C compiler-flags
  --with-build-cppflags=XXX the build C preprocessor-flags
  --with-build-ldflags=XXX the build linker-flags
  --with-build-libs=XXX   the build libraries
. . .
Some influential environment variables:
  CC          C compiler command
  CFLAGS      C compiler flags
  LDFLAGS     linker flags, e.g. -L<lib dir> if you have libraries in a
              nonstandard directory <lib dir>
  LIBS        libraries to pass to the linker, e.g. -l<library>
  CPPFLAGS    (Objective) C/C++ preprocessor flags, e.g. -I<include dir> if
              you have headers in a nonstandard directory <include dir>
  CPP         C preprocessor

None of the environment variables are set. The other options do not address library locations. The configure insists on gcc and I presume that the -lm switch tells gcc to load /usr/lib/libm.so. I cannot tell why the configure run fails to find the functions.
 
byrnejb said:
I presume that the -lm switch tells gcc to load /usr/lib/libm.so.
Click to expand...
No, it tells the linker to link with libm. GCC doesn't "load" anything (besides the source code itself of course).

Code is compiled using headers, these typically live in /usr/include (and /usr/local/include for ports), their corresponding libraries are found in /usr/lib (and /usr/local/lib). The -l just tells the linker it should the link the resulting executable with a specific library.

But as I said, /usr/lib and /usr/include are searched by default. You don't have to supply those. Most of the time configure scans for a whole bunch of things, it's not always a problem if it can't find certain things. Just because you see a "no" doesn't necessarily mean there's a problem.
 
I have managed to get this to compile, but it does not yet produce an error-free program. I am working with the developer to resolve building this on FreeBSD.

The question I have now is: are there limitations on running ptrace or other debugging tools inside jails?
 
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