[test] Improve test_emmalloc_trim output. NFC (#23342)

Also, add some assertions.

test/core/test_emmalloc_trim.c

@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <emscripten/emmalloc.h>
@@ -7,40 +8,47 @@ size_t round_to_4k(size_t val){
   return (val + 4095) & ~4095;
 }
 
-void print_stats(int cnt) {
-  printf("dynamic heap %d: %zu\n", cnt, round_to_4k(emmalloc_dynamic_heap_size()));
-  printf("free dynamic memory %d: %zu\n", cnt, round_to_4k(emmalloc_free_dynamic_memory()));
-  printf("unclaimed heap memory %d: %zu\n", cnt, round_to_4k(emmalloc_unclaimed_heap_memory()));
-  printf("sbrk %d: %#zx\n", cnt, round_to_4k((size_t)sbrk(0)));
+void print_stats(const char* title) {
+  printf("%s: dynamic heap:          %zu\n", title, round_to_4k(emmalloc_dynamic_heap_size()));
+  printf("%s: free dynamic memory:   %zu\n", title, round_to_4k(emmalloc_free_dynamic_memory()));
+  printf("%s: unclaimed heap memory: %zu\n", title, round_to_4k(emmalloc_unclaimed_heap_memory()));
+  printf("%s: sbrk:                  %#zx\n", title, round_to_4k((size_t)sbrk(0)));
 }
 
 int main() {
+  int did_free;
   printf("heap size: %zu\n", emscripten_get_heap_size());
-  print_stats(0);
+  print_stats("init");
 
   void *ptr = malloc(32*1024*1024);
   void *ptr2 = malloc(4*1024*1024);
-  printf("%d\n", (int)(ptr && ptr2));
-  print_stats(1);
-
-  int success = emmalloc_trim(0);
-  printf("1st trim: %d\n", success);
-  print_stats(1);
-
-  success = emmalloc_trim(0);
-  printf("2nd trim: %d\n", success);
-  print_stats(2);
+  assert(ptr);
+  assert(ptr2);
+  print_stats("after alloc");
+
+  did_free = emmalloc_trim(0);
+  assert(did_free);
+  printf("1st trim: did_free=%d\n", did_free);
+  print_stats("1");
+
+  did_free = emmalloc_trim(0);
+  assert(!did_free);
+  printf("2nd trim: did_free=%d\n", did_free);
+  print_stats("2");
   free(ptr2);
 
-  success = emmalloc_trim(100000);
-  printf("3rd trim: %d\n", success);
-  print_stats(3);
+  did_free = emmalloc_trim(100000);
+  assert(did_free);
+  printf("3rd trim: did_free=%d\n", did_free);
+  print_stats("3");
 
-  success = emmalloc_trim(100000);
-  printf("4th trim: %d\n", success);
-  print_stats(4);
+  did_free = emmalloc_trim(100000);
+  assert(!did_free);
+  printf("4th trim: did_free=%d\n", did_free);
+  print_stats("4");
 
-  success = emmalloc_trim(0);
-  printf("5th trim: %d\n", success);
-  print_stats(5);
+  did_free = emmalloc_trim(0);
+  assert(did_free);
+  printf("5th trim: did_free=%d\n", did_free);
+  print_stats("5");
 }

test/core/test_emmalloc_trim.out

@@ -1,35 +1,34 @@
 heap size: 134217728
-dynamic heap 0: 4096
-free dynamic memory 0: 4096
-unclaimed heap memory 0: 2147348480
-sbrk 0: 0x12000
-1
-dynamic heap 1: 37752832
-free dynamic memory 1: 4096
-unclaimed heap memory 1: 2109599744
-sbrk 1: 0x2412000
-1st trim: 1
-dynamic heap 1: 37752832
-free dynamic memory 1: 0
-unclaimed heap memory 1: 2109599744
-sbrk 1: 0x2412000
-2nd trim: 0
-dynamic heap 2: 37752832
-free dynamic memory 2: 0
-unclaimed heap memory 2: 2109599744
-sbrk 2: 0x2412000
-3rd trim: 1
-dynamic heap 3: 33656832
-free dynamic memory 3: 102400
-unclaimed heap memory 3: 2109599744
-sbrk 3: 0x2412000
-4th trim: 0
-dynamic heap 4: 33656832
-free dynamic memory 4: 102400
-unclaimed heap memory 4: 2109599744
-sbrk 4: 0x2412000
-5th trim: 1
-dynamic heap 5: 33558528
-free dynamic memory 5: 0
-unclaimed heap memory 5: 2109599744
-sbrk 5: 0x2412000
+init: dynamic heap:          4096
+init: free dynamic memory:   4096
+init: unclaimed heap memory: 2147348480
+init: sbrk:                  0x12000
+after alloc: dynamic heap:          37752832
+after alloc: free dynamic memory:   4096
+after alloc: unclaimed heap memory: 2109599744
+after alloc: sbrk:                  0x2412000
+1st trim: did_free=1
+1: dynamic heap:          37752832
+1: free dynamic memory:   0
+1: unclaimed heap memory: 2109599744
+1: sbrk:                  0x2412000
+2nd trim: did_free=0
+2: dynamic heap:          37752832
+2: free dynamic memory:   0
+2: unclaimed heap memory: 2109599744
+2: sbrk:                  0x2412000
+3rd trim: did_free=1
+3: dynamic heap:          33656832
+3: free dynamic memory:   102400
+3: unclaimed heap memory: 2109599744
+3: sbrk:                  0x2412000
+4th trim: did_free=0
+4: dynamic heap:          33656832
+4: free dynamic memory:   102400
+4: unclaimed heap memory: 2109599744
+4: sbrk:                  0x2412000
+5th trim: did_free=1
+5: dynamic heap:          33558528
+5: free dynamic memory:   0
+5: unclaimed heap memory: 2109599744
+5: sbrk:                  0x2412000