diff options
Diffstat (limited to 'ld/ld.texinfo')
| -rw-r--r-- | ld/ld.texinfo | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/ld/ld.texinfo b/ld/ld.texinfo index 77c02d6..0c5f884 100644 --- a/ld/ld.texinfo +++ b/ld/ld.texinfo @@ -3473,6 +3473,36 @@ There are a few other linker scripts commands. Ensure that @var{exp} is non-zero. If it is zero, then exit the linker with an error code, and print @var{message}. +Note that assertions are checked before the final stages of linking +take place. This means that expressions involving symbols PROVIDEd +inside section definitions will fail if the user has not set values +for those symbols. The only exception to this rule is PROVIDEd +symbols that just reference dot. Thus an assertion like this: + +@smallexample + .stack : + @{ + PROVIDE (__stack = .); + PROVIDE (__stack_size = 0x100); + ASSERT ((__stack > (_end + __stack_size)), "Error: No room left for the stack"); + @} +@end smallexample + +will fail if @code{__stack_size} is not defined elsewhere. Symbols +PROVIDEd outside of section definitions are evaluated earlier, so they +can be used inside ASSERTions. Thus: + +@smallexample + PROVIDE (__stack_size = 0x100); + .stack : + @{ + PROVIDE (__stack = .); + ASSERT ((__stack > (_end + __stack_size)), "Error: No room left for the stack"); + @} +@end smallexample + +will work. + @item EXTERN(@var{symbol} @var{symbol} @dots{}) @kindex EXTERN @cindex undefined symbol in linker script |