build failure due to zlib test in configure

[wesnm]

Building on FreeBSD fails due to an issue in configure created in #3974 when "pkg-config --libs zlib" only contains "-lz" and the expression is not guarded in some way, e.g., with "--" or prepending fixed text such as "x"

** using staged installation
expr: illegal option -- l
expr: usage: expr [-e] expression

expr: illegal option -- l
expr: usage: expr [-e] expression

[mattdowle]

Thanks.

So we're talking about these two lines in configure:

lib=`pkg-config --libs zlib`
expr "$lib" : ".*-lz$" >/dev/null

For me, pkg-config --libs zlib contains only -lz on my machine; i.e. it returns -lz only. Could you explain a little more please? Why doesn't that work on FreeBSB? What does pkg-config --libs zlib return for you?

[wesnm]

There are some differences in the Linux expr and FreeBSD. From the FreeBSD man page:

Compatibility with previous implementations
Unless FreeBSD 4.x compatibility is enabled, this version of expr adheres
to the POSIX Utility Syntax Guidelines, which require that a leading
argument beginning with a minus sign be considered an option to the
program. The standard -- syntax may be used to prevent this
interpretation. However, many historic implementations of expr,

On my FreeBSD machine:

[morganw@mercury:~/tmp$]: pkg-config --libs zlib           
-lz
[morganw@mercury:~/tmp$]: expr `pkg-config --libs zlib` : '.*-lz$'
expr: illegal option -- l
expr: usage: expr [-e] expression

[morganw@mercury:~/tmp$]: expr -- `pkg-config --libs zlib`  : '.*-lz$'
3
[morganw@mercury:~/tmp$]: expr x`pkg-config --libs zlib` : '^x.*-lz$'
4

On a Linux machine:

[morganw@media:~$]: pkg-config --libs zlib
-lz
[morganw@media:~$]: expr `pkg-config --libs zlib` : '.*-lz$'
3
[morganw@media:~$]: expr -- `pkg-config --libs zlib` : '.*-lz$'
3
[morganw@media:~$]: expr x`pkg-config --libs zlib` : '^x.*-lz$'
4

The "failure" occurred in 1.12.8 as well, but the end result was a successful build because the src/Makevars file exists in the tree, whereas in 1.13.0 the failure to find zlib causes the configure script to exit before src/Makevars is generated from src/Makevars.in. Perhaps that unconditional exit needs to be reconsidered, given that the OpenMP tests follow it. I don't know how universal the "--" guard for expr is, so perhaps prepending with a string is more portable?

patch.txt

[mattdowle]

Thanks, Morgan! Helps a lot, especially the aspect of not creating Makevars which also occurs in #4640. The Makevars started to be generated in #3984.

What I had really wanted to do originally was pass the result of pkg-config --libs zlib (i.e. -lz) through to R CMD build somehow. But I didn't know how to do that. So I put the -lz in Makevars (fixed, hardcoded) and added output to configure to tell us if it ever isn't "-lz", or if zlib isn't available, so that users know what to install. But if we're generating Makevars now, then maybe we have a way to pass it through. That would avoid needing to test for "-lz" at all, we could echo the value.

Thanks again, I think I understand what's going on now.