simplify __stdio_exit static linking logic

the purpose of this logic is to avoid linking __stdio_exit unless any
stdio reads (which might require repositioning the file offset at exit
time) or writes (which might require flushing at exit time) could have
been performed.

previously, exit called two wrapper functions for __stdio_exit named
__flush_on_exit and __seek_on_exit. both of these functions actually
performed both tasks (seek and flushing) by calling the underlying
__stdio_exit. in order to avoid doing this twice, an overridable data
object __towrite_used was used to cause __seek_on_exit to act as a nop
when __towrite was linked.

now, exit only makes one call, directly to __stdio_exit. this is
satisfiable by a weak dummy definition in exit.c, but the real
definition is pulled in by either __toread.c or __towrite.c through
their referencing a symbol which is defined only in __stdio_exit.c.

(cherry picked from commit c463e11eda8326aacee2ac1d516954a9574a2dcd)

diff --git a/src/exit/exit.c b/src/exit/exit.c
index 353f50b78ef1c9fb4b3d57c6947ec20d1f8ef620..f8e76689074992dc0b6a5afcb6f3016babc18e38 100644 (file)
--- a/src/exit/exit.c
+++ b/src/exit/exit.c
@@ -8,10 +8,10 @@ static void dummy()
 {
 }
 
-/* __toread.c, __towrite.c, and atexit.c override these */
+/* atexit.c and __stdio_exit.c override these. the latter is linked
+ * as a consequence of linking either __toread.c or __towrite.c. */
 weak_alias(dummy, __funcs_on_exit);
-weak_alias(dummy, __flush_on_exit);
-weak_alias(dummy, __seek_on_exit);
+weak_alias(dummy, __stdio_exit);
 
 #ifndef SHARED
 weak_alias(dummy, _fini);
@@ -35,8 +35,7 @@ _Noreturn void exit(int code)
        _fini();
 #endif
 
-       __flush_on_exit();
-       __seek_on_exit();
+       __stdio_exit();
 
        _Exit(code);
        for(;;);

diff --git a/src/stdio/__stdio_exit.c b/src/stdio/__stdio_exit.c
index 0fb3323489301651c14b0f516b94fb8f7b7bb3cf..e4380aaf80709c04dd7335376ca2b257b8ac3d61 100644 (file)
--- a/src/stdio/__stdio_exit.c
+++ b/src/stdio/__stdio_exit.c
@@ -21,3 +21,5 @@ void __stdio_exit(void)
        close_file(__stdin_used);
        close_file(__stdout_used);
 }
+
+weak_alias(__stdio_exit, __stdio_exit_needed);

diff --git a/src/stdio/__toread.c b/src/stdio/__toread.c
index 2e804f641dbd8a2363f88c4c08696e1f89627d08..52624f3d4f2370edbbd8d40a418ee48d06b4a98d 100644 (file)
--- a/src/stdio/__toread.c
+++ b/src/stdio/__toread.c
@@ -13,12 +13,9 @@ int __toread(FILE *f)
        return 0;
 }
 
-static const int dummy = 0;
-weak_alias(dummy, __towrite_used);
+void __stdio_exit_needed(void);
 
-void __stdio_exit(void);
-
-void __seek_on_exit()
+void __toread_needs_stdio_exit()
 {
-       if (!__towrite_used) __stdio_exit();
+       __stdio_exit_needed();
 }

diff --git a/src/stdio/__towrite.c b/src/stdio/__towrite.c
index 380ea396a133ca81ba230b2e45186aed5da2775f..0a69d926dc3c10547a00ae9f7b8517c188078c68 100644 (file)
--- a/src/stdio/__towrite.c
+++ b/src/stdio/__towrite.c
@@ -17,11 +17,9 @@ int __towrite(FILE *f)
        return 0;
 }
 
-const int __towrite_used = 1;
+void __stdio_exit_needed(void);
 
-void __stdio_exit(void);
-
-void __flush_on_exit()
+void __towrite_needs_stdio_exit()
 {
-       __stdio_exit();
+       __stdio_exit_needed();
 }