src/target: Restrict usable glibc versions

At a minimum required glibc is v2.17, as earlier versions do not define
some symbols (e.g., getauxval()) used by the Zig standard library.

Additionally, glibc only supports some architectures at more recent
versions (e.g., riscv64 support came in glibc v2.27).  So add a
`glibc_min` field to `available_libcs` for architectures with stronger
version requirements.

Extend the existing `canBuildLibC` function to check the target against
the Zig minimum, and the architecture/os minimum.

Also filter the list shown by `zig targets`, too:

  $ zig targets | jq -c '.glibc'
  ["2.17.0","2.18.0","2.19.0","2.20.0","2.21.0","2.22.0","2.23.0","2.24.0","2.25.0","2.26.0","2.27.0","2.28.0","2.29.0","2.30.0","2.31.0","2.32.0","2.33.0","2.34.0","2.35.0","2.36.0","2.37.0","2.38.0"]

Fixes #17034
Fixes #17769

1 files changed, 18 insertions, 3 deletions

diff --git a/src/target.zig b/src/target.zig
index 5ae5c420c2..acfa089034 100644
--- a/src/target.zig
+++ b/src/target.zig
@@ -11,10 +11,16 @@ pub const ArchOsAbi = struct {
     os: std.Target.Os.Tag,
     abi: std.Target.Abi,
     os_ver: ?std.SemanticVersion = null,
+
+    // Minimum glibc version that provides support for the arch/os (for
+    // .abi = .gnu).  For most entries, the .glibc_min is null,
+    // meaning the Zig minimum required by the standard library (see
+    // glibc_min_version) is sufficient.
+    glibc_min: ?std.SemanticVersion = null,
 };
 
 pub const available_libcs = [_]ArchOsAbi{
-    .{ .arch = .aarch64_be, .os = .linux, .abi = .gnu },
+    .{ .arch = .aarch64_be, .os = .linux, .abi = .gnu, .glibc_min = .{ .major = 2, .minor = 17, .patch = 0 } },
     .{ .arch = .aarch64_be, .os = .linux, .abi = .musl },
     .{ .arch = .aarch64_be, .os = .windows, .abi = .gnu },
     .{ .arch = .aarch64, .os = .linux, .abi = .gnu },
@@ -54,14 +60,14 @@ pub const available_libcs = [_]ArchOsAbi{
     .{ .arch = .mips, .os = .linux, .abi = .gnueabi },
     .{ .arch = .mips, .os = .linux, .abi = .gnueabihf },
     .{ .arch = .mips, .os = .linux, .abi = .musl },
-    .{ .arch = .powerpc64le, .os = .linux, .abi = .gnu },
+    .{ .arch = .powerpc64le, .os = .linux, .abi = .gnu, .glibc_min = .{ .major = 2, .minor = 19, .patch = 0 } },
     .{ .arch = .powerpc64le, .os = .linux, .abi = .musl },
     .{ .arch = .powerpc64, .os = .linux, .abi = .gnu },
     .{ .arch = .powerpc64, .os = .linux, .abi = .musl },
     .{ .arch = .powerpc, .os = .linux, .abi = .gnueabi },
     .{ .arch = .powerpc, .os = .linux, .abi = .gnueabihf },
     .{ .arch = .powerpc, .os = .linux, .abi = .musl },
-    .{ .arch = .riscv64, .os = .linux, .abi = .gnu },
+    .{ .arch = .riscv64, .os = .linux, .abi = .gnu, .glibc_min = .{ .major = 2, .minor = 27, .patch = 0 } },
     .{ .arch = .riscv64, .os = .linux, .abi = .musl },
     .{ .arch = .s390x, .os = .linux, .abi = .gnu },
     .{ .arch = .s390x, .os = .linux, .abi = .musl },
@@ -76,6 +82,9 @@ pub const available_libcs = [_]ArchOsAbi{
     .{ .arch = .x86_64, .os = .macos, .abi = .none, .os_ver = .{ .major = 10, .minor = 7, .patch = 0 } },
 };
 
+/// Minimum glibc version, due to dependencies from the Zig standard library on glibc symbols
+pub const glibc_min_version: std.SemanticVersion = .{ .major = 2, .minor = 17, .patch = 0 };
+
 pub fn libCGenericName(target: std.Target) [:0]const u8 {
     switch (target.os.tag) {
         .windows => return "mingw",
@@ -154,6 +163,12 @@ pub fn canBuildLibC(target: std.Target) bool {
                 const ver = target.os.version_range.semver;
                 return ver.min.order(libc.os_ver.?) != .lt;
             }
+            // Ensure glibc (aka *-linux-gnu) version is supported
+            if ((target.os.tag == .linux) and target.abi.isGnu()) {
+                const min_glibc_ver = libc.glibc_min orelse glibc_min_version;
+                const target_glibc_ver = target.os.version_range.linux.glibc;
+                return target_glibc_ver.order(min_glibc_ver) != .lt;
+            }
             return true;
         }
     }