[PATCH] fix race when building ada-lex.c

[John Reiser <jreiser@bitwagon.com>]

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PR build/22873
Prevent a race when building ada-lex.c, and any target of rules .c:.l or .c:.y.
The target should be written only at the last step, else SIGINT (^C)
can leave an inconsistent state.  Being .PRECIOUS makes it even worse.

gdb/ChangeLog:
         * gdb/Makefile.in: (.c:.l, .c:.y): Write the target only in the
         last step, and do it atomically.

[patch attached]

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From 66e71c48037729d3239d2fd30dbb92f31281763b Mon Sep 17 00:00:00 2001
From: John Reiser <jreiser@BitWagon.com>
Date: Sat, 28 Apr 2018 13:38:56 -0700
Subject: [PATCH] Fix race when building ada-lex.c

PR build/22873
Prevent a race when building ada-lex.c, and any target of rules .c:.l or .c:.y.
The target should be written only at the last step, else SIGINT (^C)
can leave an inconsistent state.  Being .PRECIOUS makes it even worse.

gdb/ChangeLog:
	* gdb/Makefile.in: (.c:.l, .c:.y): Write the target only in the
	last step, and do it atomically.
---
 gdb/Makefile.in | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 648f66d..be76928 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -2483,9 +2483,8 @@ po/$(PACKAGE).pot: force
 # Makefile.in, but that was a pretty big annoyance.
 
 %.c: %.y
-	rm -f $@ $@.tmp
-	$(SHELL) $(YLWRAP) $< y.tab.c $@ -- $(YACC) $(YFLAGS) && mv $@ $@.tmp \
-		|| (rm -f $@; false)
+	$(SHELL) $(YLWRAP) $< y.tab.c $@.tmp -- $(YACC) $(YFLAGS) \
+		|| (rm -f $@.tmp; false)
 	sed -e '/extern.*malloc/d' \
 	     -e '/extern.*realloc/d' \
 	     -e '/extern.*free/d' \
@@ -2496,13 +2495,13 @@ po/$(PACKAGE).pot: force
 	     -e 's/\([ \t;,(]\)free$$/\1xfree/g' \
 	     -e '/^#line.*y.tab.c/d' \
 	     -e 's/YY_NULL/YY_NULLPTR/g' \
-	  < $@.tmp > $@
-	rm -f $@.tmp
+	  < $@.tmp > $@.new && \
+	  rm -f $@.tmp && \
+	  mv $@.new $@
 %.c: %.l
 	if [ "$(FLEX)" ] && $(FLEX) --version >/dev/null 2>&1; then \
-	    $(FLEX) -o$@ $< && \
-	    rm -f $@.new && \
-	    sed -e '/extern.*malloc/d' \
+	    $(FLEX) --stdout $<  \
+	    | sed -e '/extern.*malloc/d' \
 	        -e '/extern.*realloc/d' \
 	        -e '/extern.*free/d' \
 	        -e '/include.*malloc.h/d' \
@@ -2511,8 +2510,7 @@ po/$(PACKAGE).pot: force
 	        -e 's/\([ \t;,(]\)free\([ \t]*[&(),]\)/\1xfree\2/g' \
 	        -e 's/\([ \t;,(]\)free$$/\1xfree/g' \
 		-e 's/yy_flex_xrealloc/yyxrealloc/g' \
-	      < $@ > $@.new && \
-	    rm -f $@ && \
+	      > $@.new && \
 	    mv $@.new $@; \
 	elif [ -f $@ ]; then \
 	    echo "Warning: $*.c older than $*.l and flex not available."; \
-- 
2.9.5