[clang] [flang] [clang][driver] Special care for -l flags in config files (PR #117573)

[David Truby via cfe-commits]

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@@ -61,3 +61,22 @@
 ! CHECK-TWO-CONFIGS-NEXT: Configuration file: {{.*}}Inputs{{.}}config2{{.}}config-4.cfg
 ! CHECK-TWO-CONFIGS: -ffp-contract=fast
 ! CHECK-TWO-CONFIGS: -O3
+
+!--- The -l flags should be moved to the end of input list and appear only when linking.
+! RUN: %flang --config %S/Inputs/config-l.cfg -o %s.out %s -### 2>&1 | FileCheck %s -check-prefix CHECK-LINKING
+! RUN: %flang --config %S/Inputs/config-l-openmp.cfg -o %s.out %s -### 2>&1 | FileCheck %s -check-prefix CHECK-LINKING-LIBOMP-GOES-LAST
+! RUN: %flang --config %S/Inputs/config-l.cfg -S %s -### 2>&1 | FileCheck %s -check-prefix CHECK-NOLINKING
+! RUN: %flang --config %S/Inputs/config-l-openmp.cfg -S %s -### 2>&1 | FileCheck %s -check-prefix CHECK-NOLINKING
+! CHECK-LINKING: Configuration file: {{.*}}Inputs{{.}}config-l.cfg
+! CHECK-LINKING: "-ffast-math"
+! CHECK-LINKING: "/tmp/{{.*}}-{{.*}}.o" "-lm" "-lhappy"
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DavidTruby wrote:

`/tmp` doesn't exist on Windows. If you really need to check the full path, you'll have to do something like adding
`! RUN: mkdir %t`
before the first RUN line, and 
` ! RUN: env TMPDIR=%t TEMP=%t TMP=%t %flang ...`
on every run line, although I couldn't quite make this work correctly when I quickly looked. 

Alternatively, just don't check the directory, I don't see any other tests in clang that check the directory that the temporary object is in.

Additionally, the driver will translate `-lm` and `-lhappy` to `m.lib` and `happy.lib` for the link line on Windows. So these should be something like "{{(-l)?m(\.lib)?}}" "{{(-l)?happy(\.lib)?}}" to work on Windows.

libomp is linked differently on Windows, and doesn't end up last with this change. I'm not sure how much that matters; perhaps limit that part of the test to Linux only (e.g. with -target=aarch64-unknown-linux-gnu; since you're using -### already it doesn't matter if that target is actually compiled or not)

https://github.com/llvm/llvm-project/pull/117573