It was reported in
<https://sourceware.org/ml/libc-alpha/2018-12/msg00045.html> that
gen-as-const.py fails to generate test code in the case where a .sym
file has no symbols in it, so resulting in a test failing to link for
Hurd.
The relevant difference from the old awk script is that the old script
treated '--' lines as indicating that the text to do at the start of
the test (or file used to compute constants) should be output at that
point if not already output, as well as treating lines with actual
entries for constants like that. This patch changes gen-as-const.py
accordingly, making it the sole responsibility of the code parsing
.sym files to determine when such text should be output and ensuring
it's always output at some point even if there are no symbols and no
'--' lines, since not outputting it means the test fails to link.
Handling '--' like that also avoids any problems that would arise if
the first entry for a symbol were inside #ifdef (since the text in
question must not be output inside #ifdef).
Tested for x86_64, and with build-many-glibcs.py for i686-gnu. Note
that there are still compilation test failures for i686-gnu
(linknamespace tests, possibly arising from recent posix_spawn-related
changes).
* scripts/gen-as-const.py (compute_c_consts): Take an argument
'START' to indicate that start text should be output.
(gen_test): Likewise.
(main): Generate 'START' for first symbol or '--' line, or at end
of input if not previously generated.
hurd's jmp_buf-ssp.sym does not define any symbol.
scripts/gen-as-const.py currently was emitting an empty line in that
case, and the gawk invocation was prepending "asconst_" to it, ending up
with:
.../build/glibc/setjmp/test-as-const-jmp_buf-ssp.c:1:2: error: expected « = », « , », « ; », « asm » or
« __attribute__ » at end of input
1 | asconst_
| ^~~~~~~~
* scripts/gen-as-const.py (main): Avoid emitting empty line when
there is no element in `consts'.
This patch replaces gen-as-const.awk, and some fragments of the
Makefile code that used it, by a Python script. The point is not such
much that awk is problematic for this particular script, as that I'd
like to build up a general Python infrastructure for extracting
information from C headers, for use in writing tests of such headers.
Thus, although this patch does not set up such infrastructure, the
compute_c_consts function in gen-as-const.py might be moved to a
separate Python module in a subsequent patch as a starting point for
such infrastructure.
The general idea of the code is the same as in the awk version, but no
attempt is made to make the output files textually identical. When
generating a header, a dict of constant names and values is generated
internally then defines are printed in sorted order (rather than the
order in the .sym file, which would have been used before). When
generating a test that the values computed match those from a normal
header inclusion, the test code is made into a compilation test using
_Static_assert, where previously the comparisons were done only when
the test was executed. One fragment of test generation (converting
the previously generated header to use asconst_* prefixes on its macro
names) is still in awk code in the makefiles; only the .sym processing
and subsequent execution of the compiler to extract constants have
moved to the Python script.
Tested for x86_64, and with build-many-glibcs.py.
* scripts/gen-as-const.py: New file.
* scripts/gen-as-const.awk: Remove.
* Makerules ($(common-objpfx)%.h $(common-objpfx)%.h.d): Use
gen-as-const.py.
($(objpfx)test-as-const-%.c): Likewise.
Joseph Myers