[libc] Elide extra space in hdrgen function declarations

[frobtech]

When the return type's rendering already doesn't end with an
identifier character, such as when it's T *, then idiomatic
syntax does not include a space before the ( and arguments.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Roland McGrath (frobtech)

Changes

When the return type's rendering already doesn't end with an
identifier character, such as when it's T *, then idiomatic
syntax does not include a space before the ( and arguments.

---

Full diff: https://github.com/llvm/llvm-project/pull/127287.diff

3 Files Affected:

• (modified) libc/utils/hdrgen/function.py (+4-1)
• (modified) libc/utils/hdrgen/tests/expected_output/subdir/test.h (+2)
• (modified) libc/utils/hdrgen/tests/input/subdir/test.yaml (+3)

diff --git a/libc/utils/hdrgen/function.py b/libc/utils/hdrgen/function.py
index bccd2c2caa2f5..24b28f7e3c7ff 100644
--- a/libc/utils/hdrgen/function.py
+++ b/libc/utils/hdrgen/function.py
@@ -81,4 +81,7 @@ def collapse(type_string):
     def __str__(self):
         attrs_str = "".join(f"{attr} " for attr in self.attributes)
         arguments_str = ", ".join(self.arguments) if self.arguments else "void"
-        return attrs_str + f"{self.return_type} {self.name}({arguments_str})"
+        type_str = str(self.return_type)
+        if type_str[-1].isalnum() or type_str[-1] == "_":
+            type_str += " "
+        return attrs_str + type_str + self.name + "(" + arguments_str + ")"
diff --git a/libc/utils/hdrgen/tests/expected_output/subdir/test.h b/libc/utils/hdrgen/tests/expected_output/subdir/test.h
index e968f92bf4e6d..20bab502e6821 100644
--- a/libc/utils/hdrgen/tests/expected_output/subdir/test.h
+++ b/libc/utils/hdrgen/tests/expected_output/subdir/test.h
@@ -19,6 +19,8 @@ type_a func(type_b) __NOEXCEPT;
 
 void gnufunc(type_a) __NOEXCEPT;
 
+int *ptrfunc(void) __NOEXCEPT;
+
 __END_C_DECLS
 
 #endif // LLVM_LIBC_SUBDIR_TEST_H
diff --git a/libc/utils/hdrgen/tests/input/subdir/test.yaml b/libc/utils/hdrgen/tests/input/subdir/test.yaml
index f325363e09cde..5bc8b29e334f8 100644
--- a/libc/utils/hdrgen/tests/input/subdir/test.yaml
+++ b/libc/utils/hdrgen/tests/input/subdir/test.yaml
@@ -12,3 +12,6 @@ functions:
       - type: type_a
     standards:
       - gnu
+  - name: ptrfunc
+    return_type: int *
+    arguments: []