ld: Don't evaluate unneeded PROVIDE expressions.
authorAndrew Burgess <andrew.burgess@embecosm.com>
Wed, 7 Jan 2015 10:51:35 +0000 (10:51 +0000)
committerAndrew Burgess <andrew.burgess@embecosm.com>
Tue, 20 Jan 2015 09:49:27 +0000 (09:49 +0000)
commitc05b575a8dfabab6af5d8586d1a5c0c67f819ac2
treed235fe75c600d32d9f4d1e6b0044ec1838299ea9
parent43d66c95c826441c64bacfa07095535ddea57a51
ld: Don't evaluate unneeded PROVIDE expressions.

When creating a linker mapfile (using -Map=MAPFILE), we previously would
always try to evaluate the expression from a PROVIDE statement.

However, this is not always safe, consider:

  PROVIDE (foo = 0x10);
  PROVIDE (bar = foo);

In this example, if neither 'foo' or 'bar' is needed, then while
generating the linker mapfile evaluating the expression for 'foo' is
harmless (just the value 0x10).  However, evaluating the expression for
'bar' requires the symbol 'foo', which is undefined.  This used to cause
a fatal error.

This patch changes the behaviour, so that when the destination of the
PROVIDE is not defined (that is the PROVIDE is not going to provide
anything) the expression is not evaluated, and instead a special string
is displayed to indicate that the linker is discarding the PROVIDE
statement.

This change not only fixes the spurious undefined symbol error, but also
means that a user can now tell if a PROVIDE statement has provided
anything by inspecting the linker mapfile, something that could not be
done before.

ld/ChangeLog:

* ldlang.c (print_assignment): Only evaluate the expression for a
PROVIDE'd assignment when the destination is being defined.
Display a special message for PROVIDE'd symbols that are not being
provided.

ld/testsuite/ChangeLog:

* ld-scripts/provide-4.d: New file.
* ld-scripts/provide-4-map.d: New file.
* ld-scripts/provide-4.t: New file.
* ld-scripts/provide-5.d: New file.
* ld-scripts/provide-5.s: New file.
* ld-scripts/provide-5-map.d: New file.
* ld-scripts/provide-5.t: New file.
* ld-scripts/provide.exp: Run the provide-4.d and provide-5.d
tests.
ld/ChangeLog
ld/ldlang.c
ld/testsuite/ChangeLog
ld/testsuite/ld-scripts/provide-4-map.d [new file with mode: 0644]
ld/testsuite/ld-scripts/provide-4.d [new file with mode: 0644]
ld/testsuite/ld-scripts/provide-4.t [new file with mode: 0644]
ld/testsuite/ld-scripts/provide-5-map.d [new file with mode: 0644]
ld/testsuite/ld-scripts/provide-5.d [new file with mode: 0644]
ld/testsuite/ld-scripts/provide-5.s [new file with mode: 0644]
ld/testsuite/ld-scripts/provide-5.t [new file with mode: 0644]
ld/testsuite/ld-scripts/provide.exp