add compiler.get_linker_id() method

this can be useful for if/elif where linker behaviors must be
considered.

For example, clang with "link" vs gcc with "ld.bfd" etc.

ci for compiler.get_linker_id() method

doc

add @FeatureNew check

Co-Authored-By: Daniel Mensinger <daniel@mensinger-ka.de>

4 files changed, 46 insertions, 29 deletions

diff --git a/docs/markdown/Compiler-properties.md b/docs/markdown/Compiler-properties.md
index 4f5ebdb..5d29dd1 100644
--- a/docs/markdown/Compiler-properties.md
+++ b/docs/markdown/Compiler-properties.md
@@ -25,13 +25,16 @@ know the operating system your code will run on, issue this command:
 host_machine.system()
 ```
 
-Compiler id
-==
+## Compiler id
 
-The compiler object has a method called `get_id`, which returns a
-lower case string describing the "family" of the compiler.
+The compiler object method `get_id` returns a
+lower case string describing the "family" of the compiler. Since 0.53.0
+`get_linker_id` returns a lower case string with the linker name. Since
+compilers can often choose from multiple linkers depending on operating
+system, `get_linker_id` can be useful for handling or mitigating effects
+of particular linkers.
 
-The compiler object also has a method `get_argument_syntax` which 
+The compiler object also has a method `get_argument_syntax` which
 returns a lower case string of `gcc`, `msvc`, or another undefined string
 value; identifying whether the compiler arguments use the same syntax as
 either `gcc` or `msvc`, or that its arguments are not like either. This should
@@ -41,11 +44,14 @@ with `has_argument`.
 See [reference tables](Reference-tables.md#compiler-ids) for a list of supported compiler
 ids and their argument type.
 
-Does code compile?
-==
+## Does code compile?
 
 Sometimes the only way to test the system is to try to compile some
-sample code and see if it works. This is a two-phase operation. First
+sample code and see if it works. For example, this can test that a
+"C++17" compiler actually supports a particular C++17 feature,
+without resorting to maintaining a feature list vs. compiler vendor,
+compiler version and operating system.
+Testing that a code snippet runs is a two-phase operation. First
 we define some code using the multiline string operator:
 
 ```meson
@@ -65,8 +71,7 @@ depending on whether the compilation succeeded or not. The keyword
 argument `name` is optional. If it is specified, Meson will write the
 result of the check to its log.
 
-Does code compile and link?
-==
+## Does code compile and link?
 
 Sometimes it is necessary to check whether a certain code fragment not
 only compiles, but also links successfully, e.g. to check if a symbol
@@ -90,11 +95,11 @@ depending on whether the compilation and linking succeeded or not. The
 keyword argument `name` is optional. If it is specified, Meson will
 write the result of the check to its log.
 
-
-Compile and run test application
-==
+## Compile and run test application
 
 Here is how you would compile and run a small test application.
+Testing if a code snippets **runs** versus merely that it links
+is particularly important for some dependencies such as MPI.
 
 ```meson
 code = '''#include<stdio.h>
@@ -126,9 +131,7 @@ if result.stdout().strip() == 'some_value'
 endif
 ```
 
-
-Does a header exist?
-==
+## Does a header exist?
 
 Header files provided by different platforms vary quite a lot. Meson
 has functionality to detect whether a given header file is available
@@ -142,8 +145,7 @@ if compiler.has_header('sys/fstat.h')
 endif
 ```
 
-Expression size
-==
+## Expression size
 
 Often you need to determine the size of a particular element (such as
 `int`, `wchar_t` or `char*`). Using the `compiler` variable mentioned
@@ -163,8 +165,7 @@ In older versions (<= 0.30) meson would error out if the size could
 not be determined. Since version 0.31 it returns -1 if the size could
 not be determined.
 
-Does a function exist?
-==
+## Does a function exist?
 
 Just having a header doesn't say anything about its
 contents. Sometimes you need to explicitly check if some function
@@ -192,8 +193,7 @@ report the function as missing. Without the header however, it would lack
 the necessary availability information and incorrectly report the function
 as available.
 
-Does a structure contain a member?
-==
+## Does a structure contain a member?
 
 Some platforms have different standard structures. Here's how one
 would check if a struct called `mystruct` from header `myheader.h`
@@ -205,8 +205,7 @@ if compiler.has_member('struct mystruct', 'some_member', prefix : '#include<myhe
 endif
 ```
 
-Type alignment
-==
+## Type alignment
 
 Most platforms can't access some data types at any address. For
 example it is common that a `char` can be at any address but a 32 bit
diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index d1fe55b..4868cdd 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -6,7 +6,6 @@ The following functions are available in build files. Click on each to
 see the description and usage. The objects returned by them are [list
 afterwards](#returned-objects).
 
-
 ### add_global_arguments()
 
 ``` meson
@@ -2050,6 +2049,9 @@ the following methods:
   such as clang or icc, especially when they use different syntax on different
   operating systems.
 
+- `get_linker_id()` *(added 0.53.0)* returns a string identifying the linker.
+   For example, `ld.bfd`, `link`, [and more](Reference-tables.md#linker-ids).
+
 - `get_supported_arguments(list_of_string)` *(added 0.43.0)* returns
   an array containing only the arguments supported by the compiler,
   as if `has_argument` were called on them individually.
diff --git a/docs/markdown/Reference-tables.md b/docs/markdown/Reference-tables.md
index 260ae30..61f4803 100644
--- a/docs/markdown/Reference-tables.md
+++ b/docs/markdown/Reference-tables.md
@@ -31,6 +31,19 @@ These are return values of the `get_id` (Compiler family) and
 | sun       | Sun Fortran compiler             |                 |
 | valac     | Vala compiler                    |                 |
 
+## Linker ids
+
+These are return values of the `get_linker_id` (Linker family) method in a compiler object.
+
+| Value     | Linker family                              |
+| -----     | ---------------                            |
+| ld.bfd    | GNU Compiler Collection                    |
+| {ld.bfd,lld} | Clang non-Windows                       |
+| link      | MSVC, Clang-cl, clang Windows              |
+| pgi       | Portland/Nvidia PGI                        |
+| {ld.bfd,gold,xild}  | Intel compiler non-Windows       |
+| xilink    | Intel-cl Windows                           |
+
 ## Script environment variables
 
 | Value               | Comment                         |
@@ -41,15 +54,14 @@ These are return values of the `get_id` (Compiler family) and
 | MESON_SOURCE_ROOT   | Absolute path to the source dir |
 | MESON_SUBDIR        | Current subdirectory, only set for `run_command` |
 
-
 ## CPU families
 
 These are returned by the `cpu_family` method of `build_machine`,
 `host_machine` and `target_machine`. For cross compilation they are
 set in the cross file.
 
-| Value               | Comment                         |
-| -----               | -------                         |
+| Value               | Comment               |
+| -----               | -------               |
 | aarch64             | 64 bit ARM processor  |
 | alpha               | DEC Alpha processor   |
 | arc                 | 32 bit ARC processor  |
@@ -104,7 +116,6 @@ These are provided by the `.system()` method call.
 Any string not listed above is not guaranteed to remain stable in
 future releases.
 
-
 ## Language arguments parameter names
 
 These are the parameter names for passing language specific arguments to your build target.
diff --git a/docs/markdown/snippets/get_linker_id.md b/docs/markdown/snippets/get_linker_id.md
new file mode 100644
index 0000000..92a91a6
--- /dev/null
+++ b/docs/markdown/snippets/get_linker_id.md
@@ -0,0 +1,5 @@
+## compiler.get_linker_id()
+
+since 0.53.0, `compiler.get_linker_id()` allows retrieving a lowercase name for the linker.
+Since each compiler family can typically use a variety of linkers depending on operating system,
+this helps users define logic for corner cases not otherwise easily handled.
\ No newline at end of file