readline: fix dependency in pkgconfig file

[jagot]

Ensure correct dependency on ncurses (and not the ancient termcap) is listed in the generated pkgconfig for readline. This is important for programs linking to readline, who will look for a (probably non-existent) termcap library, when readline was in fact built against ncurses.

[haampie]

Does this work? I see

checking for tgetent in -ltermcap... yes
checking which library has the termcap functions... using libtermcap
checking for ncurses/termcap.h... yes

[jagot]

Sorry, I was not being clear. readline builds fine, the issue is that the generated readline.pc contains a reference to termcap, although it was not actually used for building readline.

MWE

test-readline.c:

#include <stdio.h>
#include <readline/readline.h>
#include <readline/history.h>

int main(int argc, char* argv[]) {
  char* line = readline("input something> ");
  printf("Read input: %s", line);

  return 0;
}

Makefile:

all: test-readline

CFLAGS=`pkg-config --cflags readline`
LDFLAGS=`pkg-config --libs readline`

test-readline: test-readline.o
	gcc -o $@ $< $(LDFLAGS)

%.o: %.c
	gcc -o $@ -c $^ $(CFLAGS)

.PHONY: clean
clean:
	rm -f *.o test-readline

Without this PR

Tested using v8.2 because v8.3 was built with my fix, and I don't want to nuke my environment, but the results are the same.

$ cat cat $(pkg-config --path readline)
prefix=/opt/homebrew/Cellar/spack/1.1.0/opt/spack/darwin-m3/readline-8.2-4ir47ylbi7sdzlba2y2ntqm7ffkq3lto
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: Readline
Description: Gnu Readline library for command line editing
URL: http://tiswww.cwru.edu/php/chet/readline/rltop.html
Version: 8.2
Requires.private: termcap
Libs: -L${libdir} -lreadline
Cflags: -I${includedir}

$ make && ./test-readline
gcc -o test-readline.o -c test-readline.c `pkg-config --cflags readline`
Package termcap was not found in the pkg-config search path.
Perhaps you should add the directory containing `termcap.pc'
to the PKG_CONFIG_PATH environment variable
Package 'termcap', required by 'readline', not found
gcc -o test-readline test-readline.o `pkg-config --libs readline`
Package termcap was not found in the pkg-config search path.
Perhaps you should add the directory containing `termcap.pc'
to the PKG_CONFIG_PATH environment variable
Package 'termcap', required by 'readline', not found
Undefined symbols for architecture arm64:
  "_readline", referenced from:
      _main in test-readline.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [test-readline] Error 1

With this PR

cat $(pkg-config --path readline)
prefix=/opt/homebrew/Cellar/spack/1.1.0/opt/spack/darwin-m3/readline-8.3-rxoyy4phdadh5isghpfz3orodumnbaqa
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: Readline
Description: Gnu Readline library for command line editing
URL: http://tiswww.cwru.edu/php/chet/readline/rltop.html
Version: 8.3
Requires.private: ncurses
Libs: -L${libdir} -lreadline
Cflags: -I${includedir}

$ make && ./test-readline
gcc -o test-readline.o -c test-readline.c `pkg-config --cflags readline`
gcc -o test-readline test-readline.o `pkg-config --libs readline`
input something> hello there
Read input: hello there

[jagot]

Friendly bump :)