We had config machinery that determined which math functions are
available in libc. If a c math function was missing on the host system,
then the corresponding jq function would be removed from the source,
enabling the build to proceed anyway. The detection machinery was broken
in a subtle way, as was shown after glibc updated to 2.27, dropping the
`pow10` function. This caused compilation to fail.
The essential problem was that we detected whether a math function was
available by compiling and linking a small program evaluating that
function on constants. However, since gcc's optimization machinery has
special knowledge of some math functions (e.g. `pow10`), it can
optimize them away, even if they don't exist in the library and are not
linkable. That is, the following example compiles and links against
glibc 2.27, even though `pow10` has been removed:
```
int main () {
printf("%f", pow10(0.5));
return 0;
}
```
What?!
On the other hand, this program does not link:
```
int main () {
double f;
printf("%f", &f);
printf("%f", pow10(f));
return 0;
}
```
In the first program the call to `pow10` can be optimized away as a
constant expression. This requires GCC to know about `pow10` (which it
does!), but it does not require `pow10` to be in the library (and
actually linkable).
The solution is to use autoconf's machinery for detecting function
presence, instead of our own (buggy) machinery. This has the added
benefit of simplifying the code.
The bug was reported in issue #1659
This allows one to force the use of jq's builtin copy of Oniguruma
(builtin as a git submodule).
We still need to fix make dist to include that copy of Oniguruma.
Configure should still allow use of prebuilt onigurumas (whether
system-installed or in a special prefix). If these are not found, and
configure was not called with `--without-oniguruma`, then use the vendored
oniguruma module. If configure was called with `--without-oniguruma`, then we
do not build regex functionality into jq.
The CHECK_MATH_FUNC() m4 macro needs work. It should use
AC_RUN_IFELSE(), not just AC_LINK_IFELSE(), and it should #define
_GNU_SOURCE and/or other such feature macros in the prologue to get
non-standard math functions (alternatvely jq should only support
standard math functions).
Also flex is now optional.
The outputs of flex and bison are now committed. By default they get
built, but users who want to build from git can now
./configure --disable-maintainer-mode
to turn off the dependency on bison and flex.
Maintainers must, of course, commit the bison and/or flex outputs when
they make changes to parser.y and/or lexer.l, respectively.
Tests won't pass if built without Oniguruma. We don't have a way to
make a test optional yet. That will come later. For now the ability to
reduce build-time dependencies could really help some users.
jq now depends on oniguruma for regex support.
Modified configure.ac accordingly.
Added valgrind suppression file for oniguruma to prevent one-time and bounded
leaks from causing tests to fail.
Signed-off-by: Nicolas Williams <nico@cryptonector.com>
For the Mingw build we don't want to pull in the pthread DLL just
because we can autodetect pthread support. That would make the jq.exe
binary not self-contained.
William Langford
HE, Tao
Alex Ozdemir
Nicolas Williams
Erik Brinkman
David Tolnay
Doug Luce
Stefan Seemayer
Sebastian Freundt
Kim De Mey