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authorRich Felker <dalias@aerifal.cx>2015-09-29 02:44:05 +0000
committerRich Felker <dalias@aerifal.cx>2015-09-29 02:44:05 +0000
commitf3a53f095cd8ba108f8ac780da27a5ebbf4b224f (patch)
tree8f31e84a9e7e0e510fffed164235b7a1ca839d0c /configure
parent2a6e1f0f5a8811d08101df0fd72b9baa27ed430c (diff)
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eliminate protected-visibility data in libc.so with vis.h preinclude
some newer binutils versions print scary warnings about protected data
because most gcc versions fail to produce the right address
references/relocations for such data that might be subject to copy
relocations. originally vis.h explicitly assigned default visibility
to all public data symbols to avoid this issue, but commit
b8dda24fe1caa901a99580f7a52defb95aedb67c removed this treatment for
stdin/out/err to work around a gcc 3.x bug, and since they don't
actually need it (because taking their addresses is not valid C).

instead, a check for the gcc 3.x bug is added to the configure check
for vis.h preinclude support; this feature will simply be disabled
when using a buggy version of gcc.
Diffstat (limited to 'configure')
-rwxr-xr-xconfigure14
1 files changed, 11 insertions, 3 deletions
diff --git a/configure b/configure
index de357bc2..d944a47f 100755
--- a/configure
+++ b/configure
@@ -476,10 +476,18 @@ if test "x$visibility" = xauto ; then
 # - the -include option
 # - the attributes/pragmas used in vis.h
 # - linking code that takes the address of protected symbols
+# - gcc 3.x bug that wrongly claims declarations mismatch
 printf "checking whether global visibility preinclude works... "
-echo 'int (*fp)(void);' > "$tmpc"
-echo 'int foo(void) { }' >> "$tmpc"
-echo 'int bar(void) { fp = foo; return foo(); }' >> "$tmpc"
+cat > "$tmpc" <<EOF
+__attribute__((__visibility__("default")))
+extern struct a *const x;
+typedef struct a b;
+extern b *const x;
+b *const x;
+int (*fp)(void);
+int foo(void) { }
+int bar(void) { fp = foo; return foo(); }
+EOF
 if $CC $CFLAGS_C99FSE $CPPFLAGS $CFLAGS \
   -DSHARED -fPIC -I./src/internal -include vis.h \
   -nostdlib -shared -Wl,-Bsymbolic-functions \