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| author | Peter Klausler <pklausler@nvidia.com> | 2023-01-11 14:31:49 -0800 |
|---|---|---|
| committer | Peter Klausler <pklausler@nvidia.com> | 2023-01-27 16:51:03 -0800 |
| commit | aad5984b56280d7dc71a43c258c5ed349c9a239f (patch) | |
| tree | 33d8f407ee8852c075af621df29591ed3892bda5 /flang/docs | |
| parent | b4b9786f4ac4cb2d9b6e7c3ce221b06d21d6ab06 (diff) | |
| download | llvm-aad5984b56280d7dc71a43c258c5ed349c9a239f.tar.gz | |
[flang] Portability warnings for an ambiguous ASSOCIATED() case
The standard's specification for the ASSOCIATED() intrinsic function
describes its optional second argument (TARGET=) as being required
to be a valid target for a pointer assignment statement in which the
first argument (POINTER=) was the left-hand side. Some Fortran compilers
apparently interpret this text as a requirement that the POINTER= argument
actually be a valid left-hand side to a pointer assignment statement,
and emit an error if it is not so. This particularly affects the
use of an explicit NULL pointer as the first argument.
Such usage is well-defined, benign, useful, and supported by at least
two other compilers, so we should continue to accept it. This patch
adds a portability warning and some documentation.
In order to implement the portability warning in the best way, the
special checks on calls to the ASSOCIATED() intrinsic function have
been moved from intrinsic processing to Semantics/check-calls.cpp,
whence they have access to semantics' toolchest. Special checks for
other intrinsic functions might also migrate in the future in order
to keep them all in one place.
Differential Revision: https://reviews.llvm.org/D142768
Diffstat (limited to 'flang/docs')
| -rw-r--r-- | flang/docs/Extensions.md | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/flang/docs/Extensions.md b/flang/docs/Extensions.md index 31f2fda8c4cc..928fe07a7906 100644 --- a/flang/docs/Extensions.md +++ b/flang/docs/Extensions.md @@ -527,6 +527,19 @@ end module scope, with a portability warning, since that global name is not actually capable of being "used" in its scope. +* In the definition of the `ASSOCIATED` intrinsic function (16.9.16), its optional + second argument `TARGET=` is required to be "allowable as the data-target or + proc-target in a pointer assignment statement (10.2.2) in which POINTER is + data-pointer-object or proc-pointer-object." Some Fortran compilers + interpret this to require that the first argument (`POINTER=`) be a valid + left-hand side for a pointer assignment statement -- in particular, it + cannot be `NULL()`, but also it is required to be modifiable. + As there is no good reason to disallow (say) an `INTENT(IN)` pointer here, + or even `NULL()` as a well-defined case that is always `.FALSE.`, + this compiler doesn't require the `POINTER=` argument to be a valid + left-hand side for a pointer assignment statement, and we emit a + portability warning when it is not. + ## De Facto Standard Features * `EXTENDS_TYPE_OF()` returns `.TRUE.` if both of its arguments have the |