[clang] Add x86_64-redhat-linux-gnu as a platform triplet

[hoy]

Summary

Clang requires a valid/compatible installation of gcc from which it includes some internal headers. Typically clang automatically detects the correct installation of gcc from the set of gcc's installed on the system at standard locations. Adding the platform tripplet x86_64-redhat-linux-gnuthe while list of supported x86_64 triplets so that it can be used with the --gcc-toolchain option to bypass this process and force-pick a given gcc install.

[hoy]

Updating D104831: [clang] Add x86_64-redhat-linux-gnu as a platform triplet

[MaskRay]

Adding the platform tripplet x86_64-redhat-linux-gnu the while list of supported x86_64 triplets so that it can be used with the --gcc-toolchain option to bypass this process and force-pick a given gcc install.

Did you set --target=x86_64-redhat-linux-gnu? With that I don't think you need another entry in X86_64Triples.

X86_64Triples and its friends are quite clumsy and many entries are not actually needed. We should shrink the lists.

For https://bugzilla.redhat.com/show_bug.cgi?id=1824365 I think the right fix is to configure clang with x86_64-redhat-linux-gnu as the default triple.

[tstellar]

I'm curious, what kind of system are you running on where you need to use --gcc-toolchain x86_64-redhat-linux-gnu is required.

[hoy]

In D104831#2837712, @MaskRay wrote:

Adding the platform tripplet x86_64-redhat-linux-gnu the while list of supported x86_64 triplets so that it can be used with the --gcc-toolchain option to bypass this process and force-pick a given gcc install.

Did you set --target=x86_64-redhat-linux-gnu? With that I don't think you need another entry in X86_64Triples.

X86_64Triples and its friends are quite clumsy and many entries are not actually needed. We should shrink the lists.

For https://bugzilla.redhat.com/show_bug.cgi?id=1824365 I think the right fix is to configure clang with x86_64-redhat-linux-gnu as the default triple.

Explicitly specifying target or configure the default build target would work. But I thought the triple vector being updated is designed for automatic searching and minimizing configure changes across platforms. Is it not like that?

In D104831#2837795, @tstellar wrote:

I'm curious, what kind of system are you running on where you need to use --gcc-toolchain x86_64-redhat-linux-gnu is required.

One of our platforms is CentOS 7.

[MaskRay]

In D104831#2838835, @hoy wrote:

In D104831#2837712, @MaskRay wrote:

Adding the platform tripplet x86_64-redhat-linux-gnu the while list of supported x86_64 triplets so that it can be used with the --gcc-toolchain option to bypass this process and force-pick a given gcc install.

Did you set --target=x86_64-redhat-linux-gnu? With that I don't think you need another entry in X86_64Triples.

X86_64Triples and its friends are quite clumsy and many entries are not actually needed. We should shrink the lists.

For https://bugzilla.redhat.com/show_bug.cgi?id=1824365 I think the right fix is to configure clang with x86_64-redhat-linux-gnu as the default triple.

Explicitly specifying target or configure the default build target would work. But I thought the triple vector being updated is designed for automatic searching and minimizing configure changes across platforms. Is it not like that?

I am not sure about this guarantee. The list could be endless long if we supported every platform.

The right fix is to configure llvm-project with a correct LLVM_DEFAULT_TARGET_TRIPLE.

In D104831#2837795, @tstellar wrote:

I'm curious, what kind of system are you running on where you need to use --gcc-toolchain x86_64-redhat-linux-gnu is required.

One of our platforms is CentOS 7.

[tstellar]

In D104831#2838835, @hoy wrote:

In D104831#2837712, @MaskRay wrote:

Adding the platform tripplet x86_64-redhat-linux-gnu the while list of supported x86_64 triplets so that it can be used with the --gcc-toolchain option to bypass this process and force-pick a given gcc install.

Did you set --target=x86_64-redhat-linux-gnu? With that I don't think you need another entry in X86_64Triples.

X86_64Triples and its friends are quite clumsy and many entries are not actually needed. We should shrink the lists.

For https://bugzilla.redhat.com/show_bug.cgi?id=1824365 I think the right fix is to configure clang with x86_64-redhat-linux-gnu as the default triple.

Explicitly specifying target or configure the default build target would work. But I thought the triple vector being updated is designed for automatic searching and minimizing configure changes across platforms. Is it not like that?

In D104831#2837795, @tstellar wrote:

I'm curious, what kind of system are you running on where you need to use --gcc-toolchain x86_64-redhat-linux-gnu is required.

One of our platforms is CentOS 7.

Do you know why clang is not auto-detecting x86_64-redhat-linux-gnu? I'm just wondering if there is some larger problem.

[hoy]

In D104831#2839301, @tstellar wrote:

In D104831#2838835, @hoy wrote:

In D104831#2837712, @MaskRay wrote:

Adding the platform tripplet x86_64-redhat-linux-gnu the while list of supported x86_64 triplets so that it can be used with the --gcc-toolchain option to bypass this process and force-pick a given gcc install.

Did you set --target=x86_64-redhat-linux-gnu? With that I don't think you need another entry in X86_64Triples.

X86_64Triples and its friends are quite clumsy and many entries are not actually needed. We should shrink the lists.

For https://bugzilla.redhat.com/show_bug.cgi?id=1824365 I think the right fix is to configure clang with x86_64-redhat-linux-gnu as the default triple.

Explicitly specifying target or configure the default build target would work. But I thought the triple vector being updated is designed for automatic searching and minimizing configure changes across platforms. Is it not like that?

In D104831#2837795, @tstellar wrote:

I'm curious, what kind of system are you running on where you need to use --gcc-toolchain x86_64-redhat-linux-gnu is required.

One of our platforms is CentOS 7.

Do you know why clang is not auto-detecting x86_64-redhat-linux-gnu? I'm just wondering if there is some larger problem.

I'm not sure why x86_64-redhat-linux-gnu was not in the preset triples. x86_64-redhat-linux is there though. Maybe gnu libraries are not commonly used on Redhat?

clang/lib/Driver/ToolChains/Gnu.cpp

/*static*/ void Generic_GCC::GCCInstallationDetector::CollectLibDirsAndTriples(
   static const char *const ARMebHFTriples[] = {
       "armeb-linux-gnueabihf", "armebv7hl-redhat-linux-gnueabi"};
 
   static const char *const AVRLibDirs[] = {"/lib"};
   static const char *const AVRTriples[] = {"avr"};
 
   static const char *const X86_64LibDirs[] = {"/lib64", "/lib"};
   static const char *const X86_64Triples[] = {
-      "x86_64-linux-gnu",       "x86_64-unknown-linux-gnu",
-      "x86_64-pc-linux-gnu",    "x86_64-redhat-linux6E",
-      "x86_64-redhat-linux",    "x86_64-suse-linux",
-      "x86_64-manbo-linux-gnu", "x86_64-linux-gnu",
-      "x86_64-slackware-linux", "x86_64-unknown-linux",
-      "x86_64-amazon-linux",    "x86_64-linux-android"};
+      "x86_64-linux-gnu",     "x86_64-unknown-linux-gnu",
+      "x86_64-pc-linux-gnu",  "x86_64-redhat-linux6E",
+      "x86_64-redhat-linux",  "x86_64-redhat-linux-gnu",
+      "x86_64-suse-linux",    "x86_64-manbo-linux-gnu",
+      "x86_64-linux-gnu",     "x86_64-slackware-linux",
+      "x86_64-unknown-linux", "x86_64-amazon-linux",
+      "x86_64-linux-android"};
   static const char *const X32Triples[] = {"x86_64-linux-gnux32",
                                            "x86_64-pc-linux-gnux32"};
   static const char *const X32LibDirs[] = {"/libx32", "/lib"};
   static const char *const X86LibDirs[] = {"/lib32", "/lib"};
   static const char *const X86Triples[] = {
       "i586-linux-gnu",     "i686-linux-gnu",
       "i686-pc-linux-gnu",  "i386-redhat-linux6E",
       "i686-redhat-linux",  "i386-redhat-linux",