SDK: Expose C bindings

README.md

@@ -42,6 +42,57 @@ const sdk = b.dependency("opentelemetry-sdk", .{
 });
 ```
 
+## C Language Bindings
+
+The SDK provides C-compatible bindings, allowing C programs to use OpenTelemetry instrumentation. The C API covers all three signals: Traces, Metrics, and Logs.
+
+### Using from C
+
+1. **Link with the compiled library**: Build the Zig library and link it with your C project.
+
+2. **Include the header**: Add `include/opentelemetry.h` to your project.
+
+3. **Basic usage example**:
+
+```c
+#include "opentelemetry.h"
+
+int main() {
+    // Create a meter provider
+    otel_meter_provider_t* provider = otel_meter_provider_create();
+
+    // Create an exporter and reader
+    otel_metric_exporter_t* exporter = otel_metric_exporter_stdout_create();
+    otel_metric_reader_t* reader = otel_metric_reader_create(exporter);
+    otel_meter_provider_add_reader(provider, reader);
+
+    // Get a meter
+    otel_meter_t* meter = otel_meter_provider_get_meter(
+        provider, "my-service", "1.0.0", NULL);
+
+    // Create and use a counter
+    otel_counter_u64_t* counter = otel_meter_create_counter_u64(
+        meter, "requests", "Total requests", "1");
+    otel_counter_add_u64(counter, 1, NULL, 0);
+
+    // Collect and export metrics
+    otel_metric_reader_collect(reader);
+
+    // Cleanup
+    otel_meter_provider_shutdown(provider);
+    return 0;
+}
+```
+
+### C API Features
+
+- **Opaque handles**: All SDK objects are exposed as opaque handles for type safety
+- **Memory management**: The C API manages memory internally using page allocators
+- **Error handling**: Functions return status codes (0 for success, negative for errors)
+- **Examples**: See `examples/c/` for complete examples of traces, metrics, and logs
+
+For detailed API documentation, refer to `include/opentelemetry.h`.
+
 ## Specification Support State
 
 ### Signals
@@ -64,7 +115,9 @@ const sdk = b.dependency("opentelemetry-sdk", .{
 
 ## Examples
 
-Check out the [examples](./examples) folder for practical usage examples of traces, metrics, and logs.
+Check out the [examples](./examples) folder for practical usage examples:
+- `examples/` - Zig examples for traces, metrics, and logs
+- `examples/c/` - C language examples demonstrating the C API bindings
 
 ## Contributing
 

build.zig

@@ -81,14 +81,27 @@ pub fn build(b: *std.Build) !void {
         },
     });
 
+    // Static library for the OpenTelemetry SDK C users
     const sdk_lib = b.addLibrary(.{
         .name = "opentelemetry-sdk",
-        .root_module = sdk_mod,
+        .linkage = .static,
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("src/c.zig"),
+            .target = target,
+            .optimize = optimize,
+        }),
     });
     sdk_lib.linkLibrary(zlib_lib); // TODO: remove when 0.16.0 is released
 
     b.installArtifact(sdk_lib);
 
+    // Install include headers for C users
+    b.installDirectory(.{
+        .source_dir = b.path("include"),
+        .install_dir = .header,
+        .install_subdir = "",
+    });
+
     // Providing a way for the user to request running the unit tests.
     const test_step = b.step("test", "Run unit tests");
 
@@ -151,6 +164,47 @@ pub fn build(b: *std.Build) !void {
         }
     }
 
+    // C examples
+    const c_example_step = b.step("examples-c", "Build and run C examples");
+
+    const c_examples = [_][]const u8{
+        "logs",
+        "metrics",
+        "trace",
+    };
+
+    for (c_examples) |example_name| {
+        const c_example_exe = b.addExecutable(.{
+            .name = example_name,
+            .root_module = b.createModule(.{
+                .target = target,
+                .optimize = optimize,
+                .link_libc = true,
+            }),
+        });
+
+        c_example_exe.addCSourceFile(.{
+            .file = b.path(b.pathJoin(&.{
+                "examples",
+                "c",
+                b.fmt("{s}.c", .{example_name}),
+            })),
+            .flags = &.{
+                "-std=c11",
+                "-Wall",
+                "-Wextra",
+            },
+        });
+        c_example_exe.addIncludePath(b.path("include"));
+        c_example_exe.linkLibrary(sdk_lib);
+
+        const run_c_example = b.addRunArtifact(c_example_exe);
+        c_example_step.dependOn(&run_c_example.step);
+
+        // Also install each C example executable
+        b.installArtifact(c_example_exe);
+    }
+
     // Benchmarks
     const benchmarks_step = b.step("benchmarks", "Build and run all benchmarks");