configure: replace nm-based trick for sizes

The trick of declaring static arrays whose size is the value
of an integer is not working with newer gcc 10 on Cygwin,
because that compiler is rearranging the order of the arrays
and adding padding. Basically, the writing on the wall is that
this is not a good approach.

I'm switching to a different approach. By initializing a
suitable C structure (which contains character arrays) in a
particular way, we can create a .o file in which a shell
script is embedded. We can pull out the shell script and
evaluate it to get the sizes of types.

* Makefile (conftest.syms): Rule removed.
(conftest.clean): Don't remove conftest.syms.

* configure (conftest_syms, read_syms): Functions removed.
(LANG, LC_ALL): New environment variables. This is needed
because we are using tr to process a binary file;
we can't have it trying to decode multi-byte characters.
(mainline): Use new trick for obtaining variables like
SIZEOF_INT.

1 files changed, 1 insertions, 4 deletions

diff --git a/Makefile b/Makefile
index 2a87512e..dd7a2a11 100644
--- a/Makefile
+++ b/Makefile
@@ -548,9 +548,6 @@ conftest: conftest.c
 conftest2: conftest1.c conftest2.c
 	$(call LINK_PROG,)
 
-conftest.syms: conftest.o
-	$(TXR_NM) -n -t o -P $^ > $@
-
 .PHONY: conftest.yacc
 conftest.yacc:
 	$(V)echo $(TXR_YACC)
@@ -573,4 +570,4 @@ conftest.darwin:
 conftest.clean:
 	$(V)rm -f conftest$(EXE) conftest.[co] \
 	conftest2$(EXE) conftest[12].[oc] \
-	conftest.err conftest.syms
+	conftest.err