configure fails to find Tcl version correctly.

[colinhowell]

When trying to configure cicb on a recent system (MacOS 10.12.6 Sierra) running gcc 9.2.0 and with Tcl 8.6.10 installed (both gcc and Tcl installed from Macports), and configure invoked as:

./configure --prefix=/Users/colinhowell --with-readlineinclude=/opt/local/include --with-readlinelib=/opt/local/lib --with-tclinclude=/opt/local/include --with-tcllib=/opt/local/lib

the configure fails as follows:

[preceding configure output omitted]

checking for Tcl headers... found in /opt/local/include
checking Tcl version... fatal error: could not find major or minor version number of Tcl

The problem is caused by lines 454-475 of aclocal.m4, which preprocesses the conftest.c file:

#include "tcl.h"
MaJor = TCL_MAJOR_VERSION
MiNor = TCL_MINOR_VERSION

and greps for the major and minor version numbers in the preprocessed output. This doesn't work with recent versions of gcc, because when the preprocessor is invoked with gcc -E, it includes linemarkers in its output before each expanded macro. The output looks like:

# 2 "conftest.c"
MaJor =
# 2 "conftest.c" 3
8

# 3 "conftest.c"
MiNor =
# 3 "conftest.c" 3
6

Thus the grepping only finds empty lines, without version numbers.

The problem can be worked around by invoking the preprocessor with gcc -E -P, either by setting CPP accordingly or setting CPPFLAGS to -P. This will turn off preprocessor linemarkers, resulting in preprocessor output:

MaJor = 8
MiNor = 6

as expected.

[colinhowell]

For future reference, here's the change to GDB where they abandoned this method of finding Tcl. It's a very old change, from 1996.

[hoche]

Ok, I ditched all the ancient autoconf stuff and rewrite it to use CMake. Haven't tested on a Mac yet, but works on Ubuntu.

[hoche]

Ugh. Mostly works on a Mac, except where it doesn't because of libedit-instead-of-readline.